The concede option would make an excellent addition. I think that it's implementation should be carefully considered though. I think that, when it comes to 'ranked' games, such as Pantheon, perhaps the whole team must agree to concede before someone is allowed to concede without penalty. This might actually be a good way to handle it anyway.
An example use case with a 3v3 could be below... I've tabbed out the alternate scenarios.
A1-User: Player #1 hits 'Concede' from menu
A2-System: Message 'Are you sure you want to concede?'
A3-System: Yes & No buttons displayed
A4-User: Player #1 hits 'yes'
A4A1-User: Player #1 hits 'no'
A4A2-System: Game continues
-END-
A5-System: Message to all players on Player #1's team 'Player 1 wants to condede the match, do you agree?'
A6-User: All other players hit 'yes'
A6A1-User: Majority of players hit 'yes'
A6A2-CONTINUE TO A7-
A6B1-User: Majority of players hit 'no'
A6B2-System: Message to player #1 'Your team want to continue, do you still wish to concede - it will have a negative impact on your points!'
A6B3-User: Yes
A6C1-User: No
A6C2-System: Game continues
A6C3-END-
A6B4-System: Player is removed from game and has negative impact on their profile
A6B5-System: Give remaining players choice to continue or freely concede with no penalty.
A6D1-User: Both players decide to concede.
A6D2-CONTINUE TO A7-
A6E1-User: Both players decide differently
A6E2-System: Message to player #2 (who decided to concede) 'Your team want to continue, do you still wish to concede - it will not have a negative impact on your points'
A6E3-User: Yes
A6E4-System: Player is removed from game and there is no negative impact on their profile
A6E5-END-
A6B6-User: Both players decide to continue
A6B7-System: Would you like to replace player #1 with AI or not?
A6B8-User: Yes
A6F1-User: No
A6F2-System: Game continues
A6F3-END-
A6B9-System: Replace conceded demigod with AI.
A6B10-Ssytem: Game continues
A6B11-END-
A7-System: Message to all players 'the forces have darkness/lightness have conceded the match'
In the current system 'time out' window, I think all non-timed out players should be given the opportunity to click a 'kick' button or some such, so we can (if everyone votes it), expedite the players timing out, rather than waiting the full 30 seconds. Like my use case above in this scenario, we should be able to choose if the player is taken over by AI or not at this stage.
I also think, when it comes to match made games, players should be able to indicate a preference for a bot free game (at least to begin with - unless someone drops etc).
Being able to pool a teams resources together for a citadel upgrade or item purchase would be good. So, either a 'bank' we could put money into at the citadel that could only be used for citadel purchases, and the ability to transfer money to each other for strategic item purchases.