Two sided boards wich changes how each faction plays, but still works kind-of-the-same to keep the same feeling of the faction. And new spellbooks too of course.

Maybe a green and a red side to indicate how complicated the playstyle is.

This could create a variant where after everyone picks a faction, each player get to secretly select which alternative they want to use. In that way you could try to counter specific factions with alternate styles.

Create a kickstarter for a pack of alternatives for all 12 factions. That will make more people want to buy all factions and you can earn even more money.

Maybe make it a fan-based expansion? There seems to be countless fan factions on the BGG forum that you could base some of them on.

It would create endless variations without me having to buy multiple houses to store even more CW..

I know, i know, creating and balancing 24 new factions would take ages, but if you start now it will probably be just in time for me to get trough all the other content from the last onslaught!