Seems like a sound idea and I don't see any obvious reason why you couldn't do that. Especially if the PMs have a less technical background, as they often do. What you're talking about is sort of like a technical advisory or senior dev role and seems like a good thing for a company to have.

Politically it would probably be good to get each PM's buy-in and agreement about it, just from a standpoint of protecting their precious egos and avoiding a pissing match. Even though they seem to be the ones stepping on your toes a bit.