My ideal voting scheme ?
Ignoring total pie-in-the sky scenarios that I do for sci-fi writing:
I would make it legal for every citizen of the country that is not mentally demented, and who is at least 16 years old (I don't know any precedent of younger people than this being allowed to vote), to be able to vote either in person or by absentee ballot. I would also make it legal for the same people to get elected for as many offices as practicable, and make as many offices directly electable, as is practicable.
Israel allows prison inmates to vote (and in one case even let a prison inmate run, though not for an Israeli office), but that is not practicable in the US because the US voting system is based on precincts and districts.