Stef, can you elaborate on the perceived lack of "robustness when it comes to upgrades"?  What's an example problem scenario?

Someone changes a setting in /etc/pcp.conf, an upgrade happens (eg: whether in RHEL or on an image based system like a container or Atomic) which expects different defaults, or a new default ... and then things stop working.

Sorry, I don't quite see what's different here from any other /etc configuration file for any other package.

A lot of services are moving towards a setup where they have their default and/or OS provided configuration in /usr and /etc is owned by the admin, and contains admin or system specific configuration.

A classic example of this is systemd.

Hence the RFE. It would be great if we could get PCP to a maintenance free mode, where it is not broken by inattention, upgrades, or such common failure modes. This is just one aspect of that.

OK, so if I my paraphrase what you're asking for, it's so that PCP ought have a search path of pcp.conf fields, with a file in /usr and a file from /etc, the latter only to contain overrides.  This being considered as superior to the classical .rpmsave/.rpmorig style of modified-configuration-file handling.

This is a reasonable idea, but needs better scoping.  As you know, there are numerous configuration files used in pcp, not just pcp.conf.  If anything, pcp.conf is one of the most -static- in any standard installation.  (Perhaps your experience was otherwise due to the /opt relocation kludge for cockpit-bridge?
Did you know that the /etc/pcp.conf path name itself may be overridden in clients via the $PCP_CONF environment variable?)

Yes, you articulated it well.

In our case this was highlighted by the fact that missing or incorrect pcp.conf caused an exit(1) in the library. That symptom caused me to think further about the core maintenance issue, and hence this RFE.

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An interesting idea Stef, but realistically its not going to get developer attention with all the other pcp work we have on our plates.  :(  Not to discourage the idea - anyone who can, should please contribute an implementation upstream of course and those changes will flow back to Fedora through the usual update process.