I'm not sure about the overview part, but I'm thinking to get more incentive for people to sign up for AI defense (especially early on in strategus versions) have the AI pay people who sign up for their defense. Also make it so you can transfer money from strategus to your main at a rate of like 1 strat gold to 10 c-rpg gold.
Also this would give people more reason to be mercenaries, factions could have payroll for members, etc.
Seems like common sense to me, and just those two changes would bring a lot more activity to strategus.
Also, AI defenses shouldn't have twice as many people as the attackers. It should go back to single player Warband battle's for the ratios. Whoever has more troops spawns with more people in game. If they are relatively close, then it should be an almost even battle.