So here's the low down on multiple federation methods in !postActiv.

It requires rewriting too much logic and too much pulling things out to really be protocol agnostic.  So it will probably be main federation protocol OStatus forever and a day, unless upstream puts the time into hacking that out.

However, what we can do - and I'm presently working on - is making it so that all the various federation actions (sending/receiving a message, looking up users, etc etc etc) have event hooks, that you can then pile new federation stuff onto.  Then you just append or replace with whatever you need to.