Well, back to topic now...

After opening and modifying some "unification script" at least they didn't use any extra faction slots as long as there was no new "united" faction (so that wasn't unification, but annexation / absorbed faction)), and at least now I confirm, even without same unit, their FMs and generals will be converted to your own General Unit... but then, unification without immediate garrison is means asking for a massive revolt. Maybe we could do something to Pan Hellenic reform, and Pan Celtic Reform...