Amazing, I actually agree completely with every suggestion in the OP.
In addition to the above I think loot drops and equipment in general need a complete balance overhaul. Its far too common for me to get things such as champion gear from simply moving onto a tile, while I will fight an army of fierce trolls later and get something mediocre like a wooden shield. I'll beat an elemental lord and get a darkling cloak. The effort needed to take down an enemy should reflect itself in the drops. It wouldn't hurt to have drops in general be far less random while still being varied and not too predictable. Have darkling cloaks be a potential drop from darklings instead of part of a global loot table for example! Also it seems only leather cuirass drop, no other leather gear?
It is far too easy to destroy enemy faction's champions and steal their ridiculously OP gear in the early game. Equipment such as the Maul that casts shrink (unaffected by spell resists too it seems!), Berserker weapons (maul = OP) and the various pointy things of pwnage allow you to simply walk over and stomp the other factions before you research pointy sticks if you so desire. It would greatly help if these had additional conditions such as being tied to stats for their use as the OP suggests. The level barrier doesn't matter much after a few fights as a single high level champion/hero can eliminate high level mobs with ease allowing lvl 1 champions in their party to gain multiple levels per fight. I'd almost suggest something like having a limit of one champion/hero per party, to fill a general/spellcaster type role. I just don't ever seem to need to build troops, I just waltz around with my death blob of champions and thats without (ab)using the teleport spell.
I often find myself using gear I acquired at the beginning of the game over 500 turns later, with so much extra that I can't even hire enough champions to utilize it all, and generally getting disappointed with any loot drops that aren't accessories. On that note I think there should be a limit of how many accessories a hero can use, perhaps something like 3 or 5.