Map Control
There will be resource points on the map. Control the majority of them and a timer bar will start to decrease. If it's empty, you win
Let me add one elaboration to that; if you lose map control, the timer does not go away, but starts to increase. It only goes away when it's full again. If you regain control, the timer starts going down where it left off. That is, if the timer is 5 minutes, you hold map control for 4 minutes (1 minute left) and lose it for one minute, you've got to hold it for two more minutes, rather than it restarting at 5.
Style contest
The game goes for a set amount of time. You win by earning the most points. You can earn points by succesfully executing ambushes, killing an enemy commander, make a glorious charge, that kind of stuff
I disagree with this one; first and foremost, it relies upon us developing algorithms to detect "style". However, by its definition, that blocks creativity because good "style" is limited to what we've pre-programmed. I don't think it will work.
Treasure hunt
There are hidden/protected treasures in the map, win by collecting the majority/a preset amount of them
Like relics in AoE; that could work.