This is the stanza that would be added to /usr/share/X11/xkb/rules/base.xml and evdev.xml for the new layout.


        <variant>
          <configItem>
            <name>uneaf</name>
            <description>English (UNEAF)</description>
          </configItem>
        </variant>


This is the actual keyboard layout.

// uneaf custom keyboard layout                                                                                                                                                                                                               
// License: public domain                                                                                                                                                                                                                     
partial alphanumeric_keys                                                                                                                                                                                                                     
//modifier_keys                                                                                                                                                                                                                               
xkb_symbols "uneaf" {                                                                                                                                                                                                                         

    include "us(basic)"                                                                                                                                                                                                                       
    name[Group1]= "English (UNEAF)";                                                                                                                                                                                                          

    // symbols row, left side                                                                                                                                                                                                                 
    key <TLDE> { [ 9,               asciitilde ] };                                                                                                                                                                                           

    key <AE01> { [ 8,               ampersand ] };                                                                                                                                                                                            
    key <AE02> { [ 7,               bracketleft ] };                                                                                                                                                                                          
    key <AE03> { [ 6,               bracketright ] };                                                                                                                                                                                         
    key <AE04> { [ 5,               dollar ] };                                                                                                                                                                                               
    key <AE05> { [ 4,               braceleft ] };                                                                                                                                                                                            
    key <AE06> { [ 3,               braceright ] };                                                                                                                                                                                           

    // symbols row, right side                                                                                                                                                                                                                
    key <AE07> { [ 0,               parenleft ] };                                                                                                                                                                                            
    key <AE08> { [ 1,               parenright ] };                                                                                                                                                                                           
    key <AE09> { [ 2,               equal ] };                                                                                                                                                                                                
    key <AE10> { [ asterisk,        at ] };                                                                                                                                                                                                   
    key <AE11> { [ less,            exclam ] };                                                                                                                                                                                               
    key <AE12> { [ greater,         asciicircum ] };                                                                                                                                                                                          

    // upper row, left side                                                                                                                                                                                                                   
    key <AD01> { [ colon,           numbersign ] };                                                                                                                                                                                           
    key <AD02> { [ c,               C ] };                                                                                                                                                                                                    
    key <AD03> { [ i,               I ] };                                                                                                                                                                                                    
    key <AD04> { [ o,               O ] };                                                                                                                                                                                                    
    key <AD05> { [ period,          question ] };                                                                                                                                                                                             

    // upper row, right side                                                                                                                                                                                                                  
    key <AD06> { [ apostrophe,      percent ] };                                                                                                                                                                                              
    key <AD07> { [ p,               P ] };                                                                                                                                                                                                    
    key <AD08> { [ s,               S ] };                                                                                                                                                                                                    
    key <AD09> { [ d,               D ] };
    key <AD10> { [ comma,           quotedbl ] };
    key <AD11> { [ minus,           plus ] };
    key <AD12> { [ semicolon,       grave ] };

    // home row, left side
    key <AC01> { [ u,               U ] };
    key <AC02> { [ n,               N ] };
    key <AC03> { [ e,               E ] };
    key <AC04> { [ a,               A ] };
    key <AC05> { [ f,               F ] };

    // home row, right side
    key <AC06> { [ g,               G ] };
    key <AC07> { [ r,               R ] };
    key <AC08> { [ t,               T ] };
    key <AC09> { [ l,               L ] };
    key <AC10> { [ h,               H ] };
    key <AC11> { [ slash,           underscore ] };

    // lower row, left side
    key <AB01> { [ z,               Z ] };
    key <AB02> { [ k,               K ] };
    key <AB03> { [ j,               J ] };
    key <AB04> { [ q,               Q ] };
    key <AB05> { [ x,               X ] };

    // lower row, left side
    key <AB06> { [ w,               W ] };
    key <AB07> { [ m,               M ] };
    key <AB08> { [ v,               V ] };
    key <AB09> { [ b,               B ] };
    key <AB10> { [ y,               Y ] };

    key <BKSL> { [ backslash,       bar ] };
};

The keymapping is named uneaf for the left home row layout.

basically: we don't add custom layouts in fedora unless they're in upstream (or at least scheduled for upstream). So I'm going to have to defer you to 
https://www.freedesktop.org/wiki/Software/XKeyboardConfig/Development/

please file your request there and we can take it into Fedora once it's merged.

A further comment though: I think for custom layouts like this it's better if the xkb stack would read a user's home directory instead of you having to install it like a system directory. Long-term that's the better solution over having a bunch of custom layouts that we then have to maintain indefinitely.

Thanks, your comment makes sense and would solve my problem nicely.  It seems unlikely that they will change their modus operandi after all this time, however.   Maybe wayland can implement that for its keyboard mappings?

My technique has worked well enough for several years, with occasional glitches, so I can continue on as I am.

The best solution would be to buy a programmable keyboard, so that the keyboard is mapped to the custom key layout, but pretends to be a QWERTY to the system.  Unfortunately, they all have some sort of drawback, though.  Most of them still have the left side of the keyboard sloping off to the north west instead of the north east.  Talk about non-ergonomic.  And those that don't are pricey to just take a chance that they will be acceptable.  Someday, though.