I think it might be better to make hidepid=2 optional now if it’s causing so much breakage.
proc-hidepid.service can be disabled by default and how to enable it can be added to the wiki.
If System-wide sandboxing framework - sandbox-app-launcher is implemented, then hidepid=2 won’t be as important anymore as most applications can be run in a PID namespace (except the ones that break).