That's not the hard part. The hard part is getting keys moved around, expiry updated, subkeys handled—maybe having one key on the Yubikey helps with this, but I think sublet expiration is still going to be a problem.
Yup. By signing releases / commits with a particular key you're committing to maintaining possession and security of the key over the long term. For someone that loses their house key about 3 times a year, this is a big deal!