There was a very over-looked RPG/RTS game called Rages of Mages (both 1 & 2) that had a mercenary system that Rogue Hex described. Before you go out on your mission, you can visit the bar where, of course, there are hordes of mercenaries you can have come along. The cheaper they are, the more troops that'll come along (i.e. 4 Footmen for 100 gold pieces). They'll have agendas so sometimes they won't come with you. And the more often you hire them on, the higher experience gain they receive and you'll see their equipment getting upgraded. You have to hire them on for each mission but it makes the game easier. And when they die, you lose them forever (read: never can hire them back again). Is this the sort of system you mean, Rogue Hex?