Well, multiple expansions is already requested. What I'm talking about is to not be limited to only one expansion per FTM (e.g. having one song in the FTM as VRC7, but not being able to switch to something else if you want to for another song).
Multiple simultaneous expansions would solve that problem altogether: simply use just one of the several expansions you've enabled. :p
Oh wait, you said that multi-expansion NSF's are implimented already, just not available yet until all the expansion chips are done. Nevermind then. I was talking as if jsr wouldn't decide to impliment that.
I've started work on a new channel selector in the tracker that will allow picking individual channels from any chip and add it to the module, that should be the final thing until it's fully supported by the tracker. The NSF code on the other hand requires more work (as usual), but I have started preparing that too. I can't make any promises when this will be all done though.
So 'supported' is a big word, I guess one could say it's in the works but it'll be some months, maybe years, before it's finally available.