There is one good way to raise the bodyguard numbers. Make them faction heirs. After a few turns, undo the changes (or make another guy you want to have a large army, the heir). This works excellent if you have a bodyguard family member that you want to be effective in combat. The extra bodyguards will have the same chevron value, and the number wont drop if you make some other FM heir. I once had a army consisting of alot of members with atleast 80 bodyguards, just swapping the heir title between them...