Here's a small idea to add something to heroes: an adventuring tech could unlock the capability to group heroes in a single unit (a bit like a squad), creating an adventuring party, that would behave like squads as far as combat goes, just more versatile. You could create two levels of the tech, one to create parties (up to four heroes?) and one to create bands (up to eight?).
On a side note, a small UI thing missing in tactical battle (maybe already signaled): there's no way to see the statuses on a unit right now (for instance the "tangled web" that you get with some spideys) nor the number of turn they last.
Keep up with the good work!