Mercs are interesting to use, most of the time, anyway. But being the bastard cheater that I am, I modded the Descr_Mercinaries.txt to have the ability to hire ANY mercenary ANYWHERE on the map! Not only that, I also modded them to have max experiance (3 gold chevrons) and they are locked at 99 units available. Also the actually have a replenishment rate of 30 units per turn.

If any of you are interested in knowing how, just ask and I'll be more than happy to tell!