@SirVille
First, thanks for all the comments.
Red crosses - try playing with other factions

. They are for civ-specific tree branches that appear only if you play certain races (with other races, you will see disabled tech in place of Vampirism or Necromancy for example).
Buildings producing units aren't so good, believe me, it becomes a nightmare when playing on huge maps

Wonders yes, but buildings no. Spell of Awakening and Spawning Pools mess the game enough... try it, play on a Huge Map, grow, and buy Spell of Awakening to see what I'm talking about
I don't see anything wrong with spells costing upkeep or being disbandable.. on the contrary it makes sense to me.
The "kings" have been long discussed and finally, they are to be "classic" in the basic version of the mod and won't be touched. There might be a mod variation later that changes it for Multiplayer. Again, such changes to Kings only affect human player, since AI never uses kings. I really don't like giving powers to kings if they are gonna stay in a city for the whole game.
Spell ideas - I don't want to introduce more changes that involve human player only - AI is handicapped enough. And long range bombard is something very unbalancing, moreover it would make all the artillery units obsolete...
Same with the plunder... maybe for Multiplayer later, but not for the basic mod.