One thing to consider if you're going to provide a service like this:
What happens if a vulnerability nevertheless sneaks through?
The whoever did the vetting could conceivably get sued. So then they might want to take out insurance or try to protect themselves from lawsuits in some other way -- all of which is likely to make such a service even more expensive.
It has to be constrained to something reasonable. You can't guarantee the software is safe, but you can guarantee it is published by someone who is who they say they are, similar to EV certificates for domains. You can also refuse to publish packages with intentionally-confusing names.
"you can guarantee it is published by someone who is who they say they are"
Can you? Positively identifying people seems a pretty tricky and easily screwed up business.
ID's can be forged, and a web of trust requires, well, trust.
I guess such a service could say something like "we got this person's ID (and/or address)" or "here's this key's web of trust", and that would probably be a bit better than what we have today (which is virtually nothing), but it would still be a far cry from "guaranteeing it is published by someone who is who they say they are".
EV certs have a complex verification process that can involve sending a physical representative from the company down to the place of business to confirm its presence/existence.
Bitcoin trading platforms have shown that compliance with AML/KYC regulations can be performed virtually by manual verification of a valid government ID, timestamped photo, handwritten note, and other mechanisms.
A company offering this service would go outside of the keyserver and verify the ID independently. It'd be much more of a "notarized packages" paradigm rather than just "published by 1337PyHax0r-88".
It is true that even extensive manual verification processes dependent on government-issued IDs can be faked, but there's a much higher bar involved.
What happens if a vulnerability nevertheless sneaks through?
The whoever did the vetting could conceivably get sued. So then they might want to take out insurance or try to protect themselves from lawsuits in some other way -- all of which is likely to make such a service even more expensive.