I'd love to see a co-op survival mode for custom lobbies where you don't compete against another player, but rather work as a team to see how long you can last. Just make the minions we send go into the void, and have waves go past 21 so that we can see how far we can go. It doesn't need any polish to be fun 😄 Even if it's just a couple extra waves, followed by a "Ronald Finale" like Elemental TD 2 has, where the wave goes on forever and has a kill counter, and it'd be a beloved game mode.
#Co-op Survival Mode
torpid carbon
dawn folio
Wave 21 already repeats itself, and if you grab some friends and have a gentleman's agreement (no power mercs, auto till and beyond) you can comfortably get to 25/26/27 where the game just times out and the match is a draw, because people get to 20k+ value and it annihilates the poor server calculating all those units' actions etc
Also, if you custom game and only have players on one side, their sends are sent back to them (which if you kill, is more gold for you!) so you can kinda already do this