Your dedicated verifier idea seems to be quite implementable.

You just have to have a pubkey that hold itself out as a "verifier" and vouch for all the pubkeys that it follows. Actually, on second thought, you don't even need the pubkey to "hold itself out" in that way. You can just choose to treat any existing pubkey whose social judgment you trust as a "verifier".

Then all we need is a functionality in clients that lets a user set a list of the user's trusted verifiers, and then the client filters out all pubkeys that are not followed by any of the verifiers specified by the user.

Am I getting this right?