I'd say for the Cultural Victory you should have the King as champ, as he most likely organized the attacks and stuff. Also, diplomatic victory is not so cool. You do have diplomacy to help in the fights, but after all you DO need a big bad army to win it all.
Yeah, I guess King could work. Or maybe the player with the most wealth (cash, castles, etc.).
I agree that some kind of Diplomatic Victory would be pretty lame, but I also would like to offer multiple different paths to victory. Not everything has to be about killing your enemy. Then again, if we take away the duels, it's not about Elements anymore, lol. 
It's interesting about the concept of a 'Diplomatic' Victory.
When I saw that, I thought that it means that you (as an element) can be capable of doing something beyond killing, controlling wonders, and manipulating the terrain. What if there was some sort of prize for being the most 'helpful' element (not just to the other elemental allies/alliances), but also in terms of quest lines?
Perhaps there should be a minor (but MUCH longer) story quest line where you have to do all these quests to help the NPCs rebuild their land and protect them. Perhaps the final goal should be finding a way where you somehow manage to get all of the elements to ally together/stop 'fighting' and bring peace to the non-fighting elements in Outlaw City/other areas, which summons the 'REAL' god (Zanz?
) who congratulates the element and player for bringing unity to the WoE, and all that stuff.
...of course, I don't see all the elements trying to become pals due to current mechanics. XD
As for Cultural Victory, it should be the player who actually visited the most wonders - and if there is more than 1 that visited a whole bunch of them, then you'd separate it by those who actually fought for those wonders or defended them from opposing elements, as well as those who used them the most to gain resources/advantages.
