Another idea to bring back great generals!
Great generals are immortal units. When attached to a unit the unit gets the experience of the great general in addition to the unit's own experience. If the unit happens to die, the great general (but not the whole unit) respawns back in it's owner's capital, ready to re-attach. Half of all experienced earned by the unit is awarded to the great general.
A few changes would be required. Sidar wouldn't be able to turn such units into shades (I want to also block heroes from turning into shades as well to prevent certain.. Accidents). Additionally this might obsolete the Grigori heroes. Great generals might not come as freely (because I plan on making them pretty rare) or as early, but they would be immortal compared to having multiple heroes. The consequences of this would be rather interesting, as then there will be 4 kinds of units: Normal units, heroes which are best preserved and managed carefully, Great generals, which can be sacrificed but at a cost, and immortal units, which can be used freely without fear.
I never was quite fond of the finality of loss = unit death. All that does is encourage using a unit cowardly in battles it has no chance of loosing. And if that unit encounters a stack of death that can wear it down and gobble it... Well, shoulda had a mage with metamagic to see how many horsemen were nearby.
One more idea: NEw unit, Shaman. This unit can be built early on (is obsoleted by the adept), no passive XP gain, strength 2, can learn 1 spell sphere (can learn more if one manages to level them up). Gives civs a means to splash into magic if they do not grab knowledge of the ether or build mage guilds.
Finally, I am tempted to add spearmen and pikemen back in. And I might see if I can make units have multiple classes, like horse archers cavalry _and_ archers. Though the anti-promotions might need to be nerfed down to +30%, so all 3 promotions would be +60% versus hybrid units compared to 3 combat promotions.