Great question but I'm not experienced enough developer to give the best answer.
I don't know if it's possible to make this happen in the near enough future but the best would be if we could build the distro ourselves "reproducible builds". Then we can know for certain there are no added malicious modules added by the person signing the image.
Otherwise I think whatever the solution is, it must be a decentralized and censorship resistant solution, which means there must also be anonymity for the devs otherwise they can be forced to do bad things or even put in prison for working on a freedom software.
I think we can probably learn a lot from Monero's developers.
I think the best solution is probably a fair launch DAO where everyone can vote on who should be allowed to be a developer, who will do the signing, which features we want, etc.
I think others can give better and more detailed answers than me. I will look into what hydra is that you mentioned.