But in general terms, PEP is done and deployed; changing it at all is hard, changing it as radically as you propose is essentially a non-starter. It seems to me that the PEP subset is simply not sufficient for your needs; you need to use something more, whether that's more XEP-0060 features, or some other, new, protocol. But trying to change PEP because it doesn't fit your use-case is just not going to work.
Yeah, well, I'm gonna go build my own PEP, with blackjack and hookers. In fact, forget the PEP! ©