Proof of citizenship,NICS,and a fee to cover costs,approved ID,etc.
I'm fine with ID.
A NICS check to vote is a staggering idea though. We all know it's easier to get the franchise back than firearms. Many states return the franchise at the end of a sentence. Some states don't even disenfranchise local jail (misdemeanor) inmates like they do state prison (felony) inmates. For the ones that do, or don't, you've got to tell NICS which is the case- and they may not lose it in this state, but never had it returned in that state.. I don't think it would be unconstitutional, but Lord would it be a logistical nightmare.