The problem is when you are trying to verify the data down the line the original certificate (up to and including the root cert or even the authority itself) will have expired, so it won’t be possible to trust it.
You can still verify a signature from an expired certificate. With certificate transparency, you can even verify the issuance of that certificate.
Wouldn't you want to validate it for the time at which it was served? In which case you'd just an archive of the CA roots at the time.
And how do you verify that the CA roots are authentic?
The Hg history from Mozilla-Central?
Sure but that's still a third party dependency. And then you have to verify that the Firefox source is authentic. My point is there's no way to have a fully self verifying archive.