Hey Vladimir, nice to see you here!
In the post you have linked to (All Heroes for Hire from the Tavern have the entire army - #2 by HeroWO) I have explained the way heroes are currently chosen, i.e. based on SoD’s HCTRAITS.TXT only. These probabilities can be tweaked and special conditions can be introduced but I need a clear reference for that. Perhaps you can point me to relevant page(s) in FizMig or a similar resource?