Just a thought on the AI recruiting mercs thing (and I have never seen this happen so I do not know if it is possible), but what if an AI faction successfully bribed a general and the general's stack included a number of merc units?

Do these units remain mercenaries (I cannot see how/why this would change)?

Does the AI then have to pay their upkeep (I can not see why it would not unless they cease to be mercs - the AI would not "decommission" them)?

Apologies for continuing our little "off topic detour" mods, but I thought this issue worthy of further discussion. Perhaps it might be possible to split off the Mercs & AI discussion to a new thread?