Just watched the Twitch stream for arena, and it looks like a ton of fun. Though, I feel the game mode could use some changes.
Should make it so there is a set score that each team is trying to achieve and various elements to the arena grant points towards your score.
Have the game remain setup by rounds, first to 3 wins it all. Each round yields 100-150 points total for a round victory. Earn points by gaining kills and holding position on the center flag. Make it so the flag does not need to be capped and the team that is holding the flag will gain 3-5 points every second, while kills earn 10-15 points. The rounds would possibly last ~5 minutes. Another thing I seen was a gazeebo looking thing on that map. have the map contain three of these and after every ~45 seconds spawn either an instant resource gain, regen gain, dmg/defense buff for only the player to pick it up.
I feel these could add to make a very interesting game type, and obviously what they had was unfinished. Anyone have any other ideas to add to or maybe even a direction change? Arena looks like a ton of fun and there's a good chance it will be added.