Yes, modding can create autospawns. I'm not positive if the autospawns can be marked as mercs (can't be selected, die if they retreat) but if it works like Pans' autospawns they will show up in the merc squad. (I expect the merc-ness of merc units is a property of the commander and not the units.)
However, I wouldn't put this in the base game. Mercs are meant to die horrible deaths as siege fodder, not replenish with time. The merc leader is just gambling that he can get his troops killed off without dying himself, so you won't think it's worth the 80 gold to re-hire him alone. Too bad he forgot about his magic items.
-Max
(P.S. I actually don't kill mercs for their magic items. It makes me feel like David murdering Uriah. Icky.)
Re: Complete List of Mercenaries, Mercs, Mercenary
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