Well actually I guess you are back to problem 2 that Fiatjaf outlined namely that many microblogging clients would then ignore your other stuff keys. This would be a problem with my solution as well.

In Fiat's solution c, spamming other stuff into type 1 gives the  advantage that microblogger apps would appear to suck, if they don't handle these signals in a pretty way (implementing or NIP31 & NIP89 help).