Teamfight Tactics Cooperative Mode?
Idk seems pretty straightforward. 4v4 or 3v3 TFT? Basically just the same game but instead of individual lives being lost from the player themselves, lives would be taken from a much higher team life pool like of 300 or 400.
Alternatively, it could be cool to have a battlefield maybe 3x's the width of the current one and all of the players could place units on it and have some different PvE challenges or maybe more of them and be more challenging? Not sure how items would work to be honest. Could even have a team income instead of individual income to upgrade. So you spend gold to upgrade the teams income (which would take several from everyone and would increase EVERYONE's income by an additional 1 each time permanently, up to a maximum?)
Either way, I play with my friends pretty regularly and it can be a bummer when I suck and they do well and I go out first. Then my options are wait another 20 minutes for the game to end and twiddle my thumbs or go find something else to do/get better and not lose as fast.
I think a cooperative version of TFT would get a lot of play.