From where I stand, interesting combat starts at interesting choices for unit design. And interesting choices for unit design starts at interesting choices of city planning, which arise from interesting, flexible choices in economy planning, which arises from interesting, diverse, unique technical and magical research trees. One faction should be allowed to research "religion". That lets them build a church, which prohibits slavery as a technology from being available, whiich means that my ore production will suffer for the rest of the game. However, my church can be upgraded with more squares, more citizens working it, and more technology to allow for the spell "heal" to be incorporated into units, which allows me to field the designable unit "priests", providing I choose to train my citizens with 18 intelligence, with one point being gained per turn, until that unit is trained to cast that spell. If, instead, I followed religion down a tech tree of "nature worship", I will be allowed to build a grove in my city. The grove will reduce the output of the city's materials by 2/turn, since we don't cut down trees in our grove, now do we? Upgrading the grove to give it more tiles and citizens eventually allows me to incorporate the spell "entangle" into units, provided their charisma is above 16.
On the other side of the world, the trogs have just discovered "alchemy", and are faced with a choice; research towards transmutation, or towards potions. Potions are for the weak (I'm looking at YOU, Wraithes), so the trogs go for transmutation. This reserach allows them to uproot a forest tile in the city radius, and put in a smelting pit, that allows for the conversion of base metals to gold (-1 ore/turn, +5 gold/turn, and a tip of the hat to Isengard). As they improve the smelting pit, they eventually lose the -1 ore/turn, and in fact gain +1 ore/turn with enough upgrades to the smelter (We can call the top level "Mr. Fusion"), and allows units to be designed that have metal armor, provided they have a 20 strength; no problem for the 18 base strength trogs, which can crank those out in 2 turns. The wraithes, in the meantime, have spent THEIR effort on the diplomcacy tree, and have understood enough of the pre-cataclysm runes to be able to speak with the creatures guarding a nearby ruined temple, which they believe to hold an ancient device that, when placed in a city (takes 1 square), increases the output of all the shards within the city radius by +1 mana/turn, and enables the spell "firebolt" to be placed on a unit. The wraith warmaster thinks they can just take the ruined temple by force, if necessary, but the negotiations seem to be going well, and the creatures seem to be willing to let the wraiths have the artifact for just a simple sacrifice of 10 population. A bargain...
The point of my little daydream is that this is possible, but it requires a game design; a detailed, comprehensive game design that shows how all the pieces work together. What limits this game design is what the engine can do (ie, if the engine doesn't allow me to pay population in a diplomatic negotiation, then I can't do what I just said). I get that. Presumably, the designers have a design that works within the current architecture of the engine.
I'm not getting the sense of what that game design is. I'd like to see that design document. It would go a long way towards allaying fears.