Shower Idea - require two thumb prints on envelope and require envelope retained for 2 years. Also each envelope has a unique 24 digit code printed on it which is assigned to voter when ballot is sent out and must match with who signed returned ballot.
Also if voter ID not required for in person voting, then the voter will be photographed or if against religion then have fingerprint taken.
I don't think we should put our heads in the sand and think we can get a law passed requiring in person voting with photo ID in time for this election.
I think everyone should vote in person with photo ID but I don't think the pres can require that for this election but he may be able to pass an executive order putting some restrictions on the voting.