Though, the secondary doesn't necessarily have to be a maintainer or even a contributor on the project. It just needs to be someone else to do a sanity check, to make sure it is an actual release.
Heck, I would even say that as the project grows in popularity, the amount of people required to approve a release should go up.
How do I even know who to trust, and what prevents two people from conspiring together with a long con? Sounds great on the surface but I'm not sure you've thought it through.
As far as who to trust, I could imagine the maintainers of different high-level projects helping each other out in this way.
Though, if you really must allow a single user to publish releases to the masses using existing shared social infrastructure. Then you could mitigate this type of attack by adding in a time delay, with the ability for users to flag. So instead of immediately going live, add in a release date, maybe even force them to mention the release date on an external system as well. The downside with that approach is that it would limit the ability to push out fixes as well.
But I think I am OK with saying if you're a solo developer, you need to bring someone else on board or host your builds yourself.
Better to enforce good security standards than cripple the ecosystem.