ATM, Gnus is packaged as a part of Emacs. As Gnus' development cycle is not so closely connected to Emacs', updates of Gnus - whether keeping up with the Oort betas in the past or installing the current release 5.10 - are pretty complicated. It would be nice if Gnus was delivered as a separate package that can be updated separately as well. This amounts to just a little tweaking of emacs.spec.
I sympathize with your suggestion. It looks like gnus will finally get updated in xemacs-sumo in the next release for example.... On the other hand I'm not keen on ripping stuff out of emacs, since gnus is to some extent integrated into Emacs. It is not that hard to install gnus in an elisp directory of one's own or a system-wide site-lisp directory though...
Your argument is coherent - so I adjust my plea: Provide separate packages for Gnus releases that are not shipped with the current Emacs :-).
I suggest this is something for Fedora Extras (ie fedora.us). If you or someone submits a gnus package there, that passes qa, I think it will be accepted.