I think this possibility add to the game and isn't bad for balance of astral nations betwenn each others (nations with only S mages having other paths or good levels vs nations with ultra cheap S only professionnal communiants).
Alas it also adds a level of microgestion, which is never good, and strengthen an already (too?) powerful path even more.
I'd like if Illwinter can find a way to balance the reverse communion and reduce microgestion instead of simply making it impossible (ie : once the bug can be fixed, add a third communion spell to allow a mage to be an "active slave", with slightly increased requirements say S2 or 40 fatigue, allowing some form of reverse communion without the actual micro-gestion resulting from mages ID to consider).
The other option for communions, even if they worked as designed, would be to retreat the masters after they'd cast their buffs and boosters. Or to attack with them
A "Remove from communion" spell that took a mage out of communion, but left any buff effects in place could work.