Banning all apps signed by the same key is already possible. Requiring signing keys to be anonymously registered with Google would add some friction to simply rotating your signing keys when you get caught doing something naughty (depending on how much Google account creation and key registration can be automated against Google’s anti-bot protection, though), but definitely not as much as full identity verification and payment of 25 USD (even if that isn't foolproof, either, and has the annoying side effect of unfortunately slowing down small-scale freeware developers at the same time, too).