Hello there,
back in the days I was a great fan of LOMSE and I read about the project with great interest. I have a few ideas, but since I have nothing to do with modding at all, I do not know if they would be feasible at all...
That said, here's a few points:
1. I wondered if one could implement the distinction between the three different "professions" (thief, warrior, mage) in a way that is not simply adding souvereign personalities. I more or less thought of a "generic" leader in the beginning that has to choose an "alignment with a guild (or school)" when leveling up (say at level 5) instead of the five professions provided in LH. He would then complete a training in this guild (lets say freezing him for 5 turns) and change his appearance afterwards (in fact emerging as a fire giant (warrior), a fire thief or a fire mage). Problem is that one would have to mod the whole skill tree or to add a unique one for one's souvereign and I do not know if this is possible/feasible (let alone the fact that the AI has to handle it, too). On the other hand, it could make the souvereign more distinct from the other heroes...
2. I liked the possibilty in LOMSE that you could "conquer" a foreign temple as long as it was occupied by the roaming troops from the beginning and consequently gain access to another special unit. I wonder if one could implement that, say, at least for the "neighboring" faiths.
I also wanted to say that your Fire-Temple-Volcano rocks!
Cheers and keep up the enthusiasm...