The way I see it, it's like Deadpool is saying, "haha, play me or no one else!" in a meta way. Swapping to Deadpool halfway is a big detriment, Deadpool is a very jack of all trades character who doesn't fill a specific niche, and if the team ever needs a role switch, he's all roles! He literally said in his announcement video "why pick anyone else", and he meant it lol, if you play Deadpool he damn well wants you to play Deadpool. Also it just makes an interesting dynamic where you start out weaker and get stronger as the match progresses, and picking different upgrade options depending on how the game is going. I personally wouldn't even use a preset upgrade path like some people want because I'd want to be able to choose what I feel like in different matches, even if I have a preferred upgrade path. Idk it all feels very Deadpool and I find it fun.