No amount of extra rewards is going to make anyone put up with being 5v1'd or 10v1'd. None. So this is how you fix warmode. If your zone imbalance reaches a threshold of one faction out numbering the other faction by lets say 3-1. Then the outnumbered faction in that zone would receive a buff, for example:
Courage of the Alliance: Health and damage increased by 150%.
That is 150% for a 3-1 ratio, increasing by 50% for each tick of imbalance. Yes that means if you are outnumbered 10 to 1 and your town is completely overrun (this happens often for alliance) you would receive a zone buff to your health and damage of 500%.
No way! That's totally broken and OP! Everyone would turn on warmode just to be a God mode player!
Thaaaaaaaat's riiiiiiiiiiiiiiiiight. And once people turn on that warmode so that they can be a PvP raid boss, they will quickly notice that buff powering down as more people turn it on. Or just Horde fleeing the zone rather than fight you.
Also, they'd just have to make it so the buff didn't work in PvE.
And then balance was restored. You'd have your level playing field, one way or another.