does anybody already attempted this or knows a mod that did something similar?

the idea being to have smugglers & headhunters hireable by anyone, but unique on the GC map - i know about unitmodding and how to make them unique in their faction - but how to make them unique on the GC map? - what i need is some sort of check if any of the other variants already exist, that also registers when those units get defeated, to make them available for the other factions to hire them, while the faction that had them hired get's a cooldown till they can hire them again (if noone else did ofc)