Use the machine-read forms like the SAT & ACT use, only on stiffer cardboard to avoid accidental folding. The voter is given a form and a number 2 pencil and goes into the voting booth. A giant copy of the form is mounted in the booth for him/her to use in reference, along with whatever explanations may be needed. He/she fills out the form, making whatever erasures he/she wishes to. When finished, the voter drops the form into a slot in the booth so nobody can see his/her answers.

The paper ballots can be read very quickly by machine. Each stack is read twice for validation. Any discrepancies are resolved by a recounting until a consistent result is obtained. The machine is the final arbitrator of readability. Nobody is permitted to interpret the results. If the marks are not legible by the machine, then the vote does not count. The ballots remain a permanent record for recounting if necessary.

Alternatively, the voter does not actually handle the form. Rather, he presses buttons on the giant version of the form until he likes the result. Then, when he pushes the "DONE" switch, the form is mechanically marked with ink according to the buttons that he pushed and drops into a slot. Simple to validate the accuracy of the machine. No software rigging possible.

Simple, low tech, cheap, reliable, secure. Why not?