If one were to go around messing with the recruitement possibilities through the EDB, would a fairly good rule of thumb be that if an unit can be recruited through the merc pool it ought to be also recruitable from barracks for most factions ? After all, if they're willing to take cold hard cash to fight some weird foreigners, they're probably willing enough to sign up through the "regular" channels too... Plus there's already a merc skin that can be used without further ado.

Hippeis immediately spring to mind as one example. They're pretty much the Hellenic parallel to the Mada Asabara (whom just about everyone and their dog can recruit either as regionals or faction units) anyway, right ? The mounted colleagues of the Hoplitai. And by extension the same would really go for the Hippakontistai too, even if they now aren't available as mercs, seeing as how they're really just jumped-up Akontistai on horseback (okay, not really, but you get the idea - the Hellenic equivalent of the likes of Nizakhar Ayrudzi and Mada Nizhak Asabara)...