I didn't propose it, because it is very half-baked, but an interesting #Mastodon feature, or maybe #ActivityPub inbox feature, would be to supervise or moderate a different account.
For me, I'd like Clover to eventually have an account, and I'd like the ability to read everything until the account is one-way optioned into a full account that no longer allows access like that.
See, half-baked.
Although, I haven't really used the "locked account" stuff, so maybe a lot of protections exist...