Haven't really kept up with the thread, but I think you are over-thinking it a bit fips.
Start each map with defenders at x5 and attackers at x1, every time the defenders lose a base they lose a multi, every time the attackers capture a base they gain a multi. The benefit of this system over a timer based capture system is that most fighting in conquest (i.e. 2/3rds of the round time, assuming defender respawn timers stay extremely low) will occur when each side has 2-3 flags in there control, so most people would be on a x2 or x3 for that time. Population is the key to conquest, and nothing kills pop like the perception that one will have to spend 20+ minutes on an x1. With a timer based system I feel that most attackers would lose their multi once the defenders are down to a couple flags, then be faced with fighting on a x1 for the rest of the round, or quitting to battle.
The other main problem with conquest mode (specifically in NA) is that we really don't have the pop for it. Right now it's just killing the siege server for the few that still play, and even with a decent multiplier system I really don't see the battle bros becoming fond of it. Many NA people really enjoy one life per round, and alt-tabbing when they die. They want to check ts links, or browse the forums, a game mode that does not allow significant down time in between lives will probably never gain much traction in NA.