I like the idea of more end game winning conditoins.
What would be some that you guys would like to see?
To bring things back to talk about Sorcerer King...
Looking at a past dev journal touching on similarities between SK and Star Control 2 had me thinking. One of the things that I loved about SC2 was the dialogue and interactions you had with the various quirky aliens. SK has the beginnings of this, with a good cast of factions, but I feel like there should be more there. You do some quests for them, and then they just give you some randomized gifts now and then. I'd definitely like to see more interactions available with them, especially so that they remain interesting even after hitting 5 favor with someone.
More interactions between the rivals would also be neat, beyond "We hate X." An example: you can learn from the Keepers of the Flame about the truth behind the war between the Frozen Realm and Ice Lords. It'd be neat if you could do something with that to mend things between the two.
To tie this in with the win condition ideas, how about a quest/diplomacy victory involving finding a way to destroy/neutralize Curgen's Bane, rather than killing the SK directly? This could require the combined efforts of a number of rivals, dependent on map size, and doing challenging quests for each of them to contribute to the victory.