Need more than a recount of fake recounts
I’m not sure I understand what an envelope / signature audit could do.
Yes, you might find 100,000 envelopes with bogus signatures. But then what do you do? The envelopes are not matched to ballots anymore because the ballots are secret vote. The ballots were removed and put in the stack. They become anonymous at that point.
So you might want to erase 100,000 votes, but which votes do you erase? You could never randomly erase ballots. Equal Protection clause would stop that.
So I don’t know what can be done with an envelope audit. Though . . . it might certainly cause the legislature to act.