Seriously, so many of them were about playing the game. And I like playing the game! Time in zones, # of captures, play or win cames, it’s nice!
A few suggestions to provide challenge while still being fun:
Kill X spartans challenge - In all my games, I saw only a few people get more than 8 kills in a single game. The amount of time required for a 50 kill challenge is extreme in that regard, potentially requiting 15+ Land Grab matches to accomplish.
Remain in zone for x seconds - This felt incredibly easy. Even a 60 second occupation time was done in a single game (and it’s on the same XP tier as 50 kills). Maybe a 2 min. occupation time would guarantee a reasonable need for a couple games.
Double kills - I think this game would be good for this kind of challenge. Don’t go crazy and say you need 10 for the 400 xp tier, but double kills are possible with people huddling together in zones.