In Strat 1.0 every battle had full rosters because the xp was so good that any diplomatic ramifications were ignored in favour of xp... so how about this.. when you are fighting for an AI fief you get the equivalent of a 6x or better multiplier as well as the bonus xp for people dying and equipment and so on. This will accomplish a few things...
1. people will be a lot more eager to sign up for neutral fiefs.
2. only those who really want the attacker to succeed are likely to sign for the attacker. and
3. normally the defenders get bored an kamikaze due to lack of organization or caring... but with this system, the longer the battle lasts the more xp the defenders get... the attackers have no incentive to prolong the battle, but the defenders do, and the best defenses are usually the ones with the patience to stick together and hold the village rather than running around and getting killed.
this means that there will be a lot more incentive to not only fight for the AI, but to fight well and coordinate your efforts.
as for villages paying gold... i really dont think it matters... strat gold only matters to the people who invest time in strat, but the xp matters to everyone who plays crpg, so youll get a ton more people who are interested in signing up for neutral faction which might get them into strat a bit more in general, even though xp for signing up with factions isnt great.
p.s. it is slightly abusable in the sense that a faction could "take one for the community" and launch a 1/3 attack against a fief and then just camp while everyone gets xp... but since there will be so many people wanting to participate, it seems there is about a 99.999999999999% chance that an admin or at least someone who is not friendly towards that clan will attend and perhaps a peasant counter attack will hit the offending clan as the peasants would become so cocky after defending their village so easily... or a dark force could take retribution.