For the former: just use the balancing as it’s done in arcade and realistic, because the mode’s only real change is that you have dynamic capture points. It’ll still work. Yes, it gives an advantage to fast vehicles on the attacker side, just as it gives an advantage to snipey hull down bois on the defender side. Easily changed by having some map variety where the role of defender changes based on where the map is supposed to be and how that particular bit went in the war.
The latter part though; fracturing the playerbase. There’s generally plenty of people in RB and AB, and the whole excuse of “ya but but mah queue times” that Gaijin trots out is 100% grade-a steer kaka. Let’s be real, if suddenly more than half the player base suddenly does nothing but play Advance that should be a rather firm signal that this is what the playerbase wants.
Come to think of it I think that’s probably why it was shut down in a hurry because random battle queue times went up - and instead of seeing that as the signal it was, Gaijin just went nope, ain’t nobody messing up our queue times!