I suggest to change the rules about Isra and Vidomina. Its an unnessesary limit that you are not allowed to attack with them if you get them from prison. It can really ruin your plans. I think the rule should be that if you get them from prison with exp necromancing you have to dismiss all the skeletons they make. As I understand the current rules you are allowed to use them with no limits if you get them as lvl 30 prison heroes. That needs to be changed too.
I also suggest that it should be allowed to use sir Mullich in battles for the next 2 days if you get him from prison.
Considering how much is allowed in HW rules (necromanzing, dd, fly, upgrade from cons and hives, log specs) I also find the restrictions on lvl 4 magic heroes unnessesary. It will be on very rare ocations they will shift the balance compared to the other things.