Next step: ending the secret ballot.
Who will guarantee that ballots will not be stolen and/or replaced from the mail?
Absentee balloting should be returned to it's original intent, that is if you can demonstrate you cannot make it to the poles on election day. Anything beyond that is an invitation to vote fraud.
If someone were to discrete informs you that something unpleasant is going to happen to you unless you hand them a "properly" filled out ballot and let them inspect it before they mail it in, just how 'secret' would your ballot be?
I would like to see Congress pass some model legislation for absentee ballots providing that states should provide a convenient means by which state officials could certify that a person went into a booth with a blank ballot and unsealed envelope and came out with a sealed envelope. States that did not want to participate in such a program would not be required to do so, but those that did so would reap reciprocal benefits from other states that did.