I don’t agree, if you want to remove friction, you have no choice to “trust” at all certainly level where you import your key.
Or else you are left with remote signers and add a middle man.
Even if you go the route of removing the notion of master key and simply solidify the Npub and do expandable signing keys, you re-add an extra layers of management.
Maybe a system that audit and vouch for apps in which users would have bigger trust to use their master key, no other options
