I would like to see Ready Check being part of oUF's core, though. I don't know if it's just me, but It never seemed to update properly. At least hiding itself after a certain period of time - after someone performed a ready check - did not seem to work sometimes. And after all this is definitely an unit frame element.
Have you thought about giving party pets and all things alike an own .. err, term(?!) which can be used to address them, like you did with party and raid instead of the "GetPArent() .... whatever" thing it was in the past?
I still think it's quite annoying that frames like party pets inherit all and everything from party and one has to "ClearAllPoints()" etc. everything to clean them up. But maybe I'm just doing it wrong - spawning them through xml, atm.