I propose to add in the game collab system. Ie two people can do one challenge, and thus, challenge will be faster and will be more profit. Do you like this idea?
To me, you could have two players working together to clear as many stages as they can. This would mean that you need to make more levels, or edit existing ones, but you could also add a co-op feature to levels, so that you could do workshop levels in co-op. How this would work would be to have one map from one player's selection of co-op levels that they've made or downloaded, and play that one, then do the same thing with the other, and keep rotating. You could do something with more players using this method as well, just have randomly selected order for what maps they have. If they don't have any levels for bronze, or whatever difficulty they're on, then they would just do normal levels until they have a workshop level for the difficulty.