uCoin is already compliant with what you propose, because it can be reduced as a “pubkey selection” problem which is a pure human decision and is not relevant at uCoin software level.
Because uCoin have no idea what a human is, this is an undefined term. uCoin only recognize public keys and relations between them. The WoT rules are here as requirements to avoid massive cheating, and will work even if pubkeys are selected during assemblies. The assemblies would just be an help for people to have confidence in the existence of a unique human behind the key (which is a thing that remains to be proven - I am not convinced).
But If you really want vertical control over the pubkeys that can be members of the community, then you will have to make another software, or at least fork it to behave this way.
Just my opinion.