Improvements can now upgrade to two different things depending on a prereq. I noticed that Command Post upgrades to War College and Warrior Temple. The way it chooses which next option is possible is with a prereq. That means for me specifically that Ivory Towers can have a Dungeon do this:
Level 1 Dungeon
Level 2 Upgrades Dungeon to Conjurer's Circle or Beast Den
Level 3 Upgrades Conjurer's Circle to Necromancer's Circle or Demonic Circle; Upgrades Beast Den to Lycanthrope's Den or Serpent's Den
I planned this system back in beta 2, but then it was not possible. Now it is! The way you will choose the different paths will be decided by the quest line you must go through to advance Ivory's Unique technology. I can also have current upgrades be replaced by Ivory options. So, when you get to level 2, you will have 4 choices. Town, Fortress, Conclave, Tower. Choosing tower is only an option once you have completed the first quest. The mod will be balanced with the normal game, so you have the other three options, but you need at least one tower city to continue the story. I have to figure out the balance factors still, but basically I want to make trained units weak little minions. I want all your units to either be from lairs or summoned. Now I have the control I need to integrate the mod within the current game.
For everyone else, this means mods can be even more compatible. We can have crazy buildings and units that all upgrade from the same buildings and yet never meet. I just love this new option, if you couldn't tell. The idea may not be new, but it is finally possible. Thanks Stardock!