I'm unsure how to do it. From a technical standpoint, it's not that difficult, but enforcement is a bear and may cross numerous lines.

What first occurred to me is that we tie the ability to get social programs including Social Security to voting, and that if you cannot vote for some reason, it is excused via judicial means. Of course, this would require pretty serious bolstering of the ability to vote absentee.

Frankly, what you said regarding Australia would probably be sufficient. Most would vote.