The combat engine has everything! Slam people into spikes. Drop them off cliffs. Roots. Counter-attacks.

But one mechanic that's noticeably absent is attack-of-opportunities. I think it could add another layer of tactics if there were an ability/stat (or new class) that let melee units do standard attacks against enemies trying to run away/past squares within melee range. The number of attempts per turn could increase with levelling, or simply deplete from existing reflexes/counters stats.

If it's put on some of the less used, slower, weaker melee classes they could be used to control space and protect other units by taking a swipe at anything that tries to run past.

With AoO slower/weaker melee units could excel at protective duties and space control, rather than trying to compete with the devastating offense/speed/survivability of the heavy hitters like Golems and cav.