They should opt for a Homm city building style with fixed cities with fixed size like Aow1 but many buildings to improve them and the chance to raze and rebuild them. Aow 1 was too barebone with just upgrade, Wall, pillage and raze.
Simcity is not adding any depth to the game. All this buildings inside cities just slow down unit production and not adding much to the game. Its basically numbers going up.
Lets leave besides the logic (how come you can develop cities in span of few days, during war - but they was not able to even construct peasants hut during hundreds years of prosperity), what is the strategic decision behind NOT building a barrack, temple or builders hall everywhere ? While it have a LOT of sense to consider building or not walls in forward placed city, to allow easier recapture (without having to bring slow ram, or siege units).
HoMM style is only fun for the first city, if you have them more, say 6x its only wearing to slowly build them all up. I finished today Caster of Magic (almost win, bastard kill my wizard in undefended main city - yes im moron, but i didnt expect him to be able bypass my doomstacks), and i delegate all building construction to Grand Vizer (AI).
Im not against the idea of building structures in city per se. But it should affect the strategy on the main map.
f.ex. if I am able to build farms; its represent by fields on the perimeter of the city; and the enemy unit stack could occupied thouse and heal his units, or just gain some resources, without even attacking my city.
This would create a decision if I really want to build that in this place.
f.ex.2 if I build Temple in the city; the population happiness will increase; but enemy could gain advantage if the god favor him more.
Now you would have to consider, if its worth it if your strategy assumes razing all captured cities (with temples) for quick money income in near future.
f.ex.3 if i build workshop, to increase production, then the magic potential in city drop.
This could be an issue if the city was a summoning point for all my magic troops, because now they cost more mana support, or they are summon 1 turn longer.