At a technical level it's straightforward. Repo maintainers maintain their own vouch/denouncelists. Your maintainers are assumed to be good actors who can vouch for new contributors. If your maintainers aren't good actors, that's a whole other problem. From reading the docs, you
can delegate vouching to newly vouched users, as well, but this isn't a requirement.
The problem is at the social level. People will not want to maintain their own vouch/denounce lists because they're lazy. Which means if this takes off, there will be centrally maintained vouchlists. Which, if you've been on the internet for any amount of time, you can instantly imagine will lead to the formation of cliques and vouchlist drama.