I would like to propose an enduring confrontation game mode where essentially it is a game running at all times with players being able to join and leave as they please.
Basically like invasion but each team can capture points so the defending team could counter attack and push back the attacking team then becoming the attacking team. The game would never end because once a team captured all the caps they would be defending that cap from a counter attack until the team that has no points knocks them off the point.
Some flaws with that system would be that the team that is pinned and has no caps could get spawn camp abused or just never be able to break out. To solve this I would suggest having the caps on the ends be very easy for the pinned team to cap for example have the spawn for the pined team overlooking that cap or in some sort of advantageous place.
Another option would be to increase the ammount of possible spawn locations when you own less caps, or have the spawns shift around dynamically so you could never spawn camp for long.
I like the idea, but I think that if one team is pinned for certain period of time, match should close and declare one side a winner to make sure, that players won´t start to feel like playing/progressing through the match is just pointless because they are simply bound to be pushed back.
Also, from WT experience I must point out, that server hamsters (no matter if old or freshly drafted from gulag) never really liked this mode which often results in server instability/huge lag/bad fps optimization in match.
Developing that would probably take quite a some time and resources.