Key management by the OS itself, or at least by some system app. Most people have multiple devices anyway, and they won't ever need to worry about manually securing their keys. You would be able to sync your keys with multiple devices by scanning stuff. If there are secure elements in the device you are using, then key management becomes even safer

This OS could support/develop some open protocol for an ecosystem like the Apple one

Also, built in nostr, Bitcoin, and reticulum support etc

Imagine how much easier it would be to develop nostr apps and other nostr like things if signing and encryption using user keys were features of the OS itself