I'm not sure about models other than ClearCom and
TRS, but those have multiple (at least 3) outputs on the Main Station so a splitter may not be necessary.
I think at a minimum, one should plan for SM,
LBO, SoundOp, SR Deck, SL Deck. Then center of
auditorium for LD or SM for tech purposes, spots, flyrail,
etc.
A ClearCom system is not the best solution for backstage paging and program feeds to dressing rooms and
greenroom. I would keep everyone on the same
channel, but pull two-pair wire in all permanent installations, (unless using a digital system).