Well, I was thinking,
Why not make an event where GM's help the lose faction?
It's like where GM's with their OP equip and skill join out in Janus, Turnpike or even Caergate.
Sure the wining team gonna complain "WTF that's not fair!", but this gonna make ppl say this to, "Hey GM's helping those faction, let's join that one". And thus the balance will be balanced again
( a little bit naive isn't it lol )