On the topic of an Ice Climber reboot, I'd really like to see them go all out (never going to happen but still). I've mentioned on past Ice Climber threads a few times that I'd love to see a big co-op adventure/platformer.
Playing BotW made me realize how little is done in the icy terrain, it's practically undiscovered territory in gaming, and I'd like to see more of it.
I think a Spelunky-type game, or even a Journey-type game could do the Ice Climbers well, too. Really there's a lot of ways that franchise could go, if they ever attempt to rediscover it.
That being said with the giant list of games that need to be addressed, I'm not holding my breath.
Kirbeh
I had a similar idea for costumes, and I really like it, but someone brought up that there may be legal issues or whatever, especially with 3rd parties. Don't know if it's true or not, but letting people make their own costumes seems like a no-brainer to me, so I'm guessing there's something there stopping it.