It would be nice if absentee voting were encouraged by the system as that would tend to minimize the effects of such schemes. Think a good start on this would be to replace the term "Absentee Voter" with "Early Bird Voter" and have the government provide postage paid envelopes for mailing in the ballots (the $1.00 IRS Refund Contribution Option could be a potential source for funding this). GOTV activities should be more focused on having people register as Early Birds throughout the campaign rather than the frantic activity during the closing days (which of course could still occur).
The major advantages to the voting public would be much shorter lines at the polls and, for the Early Birds of course, no hassle getting transportation to the polls & waiting in lines.
The system should also provide positive feedback to the Early Bird voters confirming receipt of their ballot via the voter's designated choice (e.g. secure email, tel., or USPS).
With the advanced state of the hacking art, Early Bird Voting via a secure internet link is probably not in the cards although quite a few folks do the majority of their financial transactions via this mechanism.