Some ideas :
- Introducing basic diplomacy would be nice (OK, It has certainly already been said, but this is how I see it
). Peace, alliances (maybe allied victories), the possibility to offer units to another pretender (same way as gold and crystals- of course it's possible to refuse). And the possibility to cross allied provinces.
- Possibility to move the capitol city to recruit capitol only units nearer to the front (for example). Of course, it shouldn't be free, it should have a high gold cost, and maybe require the presence of the pretender working at it for some turns in the new capitol (or the prophet).
- Heat/cold should modify units characteristics instead of being an economic factor. Or maybe both. A bit like cold blooded units, units from a race liking cold should be very disadvantaged in hot provinces. Temperate units should have smaller characteristics reductions in cold/hot provinces. Don't know if morale, strength, hps or something else should be affected, but you get the idea
.
And I like magnate's idea to have magically summoned buildings. It should replace the non-existing city improvements and province enchantments and be managed in the magic sites lists. One commander could destroy them. I.E. : death magic would allow an assassins guild (permitting to recruit assassins), fire should permit a volcano (increasing hotness), etc...