Noticing that the AI often has hundreds of units, many of which aren't a threat, but the AI does raid/steal resources with them, it's what should be done, but it's annoying to deal with and really not fun. This is a problem that is common in Stardock games, GalCiv II had this problem as well.
This is probably just me stating my preference to move fewer, more powerful units.
Solutions:
buff militia.
Introduce a system where troops need to extra gold to be maintained based on their resource consumption, and a system where going over a limit of units built (not champions/summons/special units- but trained units) costs extra maintenance- the cap on those extra units should be sum of the levels of all your cities+ level of your sovereign+ bonuses for certain traits (maybe add this to governor) .
Do other folks find it fun to chase down 6-7 stacks of minor units? I know it's a way for the AI to be better than a human, because the AI doesn't have an aversion to being annoying, but it is annoying.