making them start out weak as fuck and actually require weeks of leveling to get good is a simple solution.
Are Mercenary really that powerful??
Yes. Amassing mercenaries can end fun and fair tc/skirmish fights in matter of seconds. If bank interest hadn't given us so much money, there wouldn't be that much mercs but when there would they would bring fast and undeserved victories.
would be awesome to have everyone be able to hire 5 mercs(or slaves) no matter what charisma is. (lulz, huge populated wars)
Things like "OH MY FUCKING GAWD DELETE MERCS CUZ I RAGE AND MAKE NO SOLUTION JUST RAGGGEEE CUS I GOTZ KILLED BY MERCS!!!!!" Will be easily won by the arguement "Well why don't you buy some yourself and fight them?" and "I don't have the caps" Will also be pointless as the arguement by: "Well why don't you go get some caps to buy them then?"