Here's a few ideas. Add yours in the comments.

• "we mean it" amendments for the 1A and 2A
• add a house to Congress where people get called up (not elected) like for jury duty for each bill, and get given 5 days to review and vote, and bills must pass all three houses
• require that the Secretary of the Treasury cut spending across the board when Congress deficit spends / let POTUS line-item veto when Congress deficit spends
• codify jury nullification so it is always ok to argue for it
• make it hard to fire police for refusing to follow unlawful orders
• obviously require paper ballots and tamper-evident paper and digital audit trails
• cap absentee ballots at .5% of registered voters
• disallow mail-in voting (except requested absentee ballots as above)
• limit voting to three days -- no weeks of early voting
• term limits: representatives get 1 term, senators get 1 term, legislature members get two max, governors get two max, presidents get to max
• senators should be elected by the legislatures again
• being senator should be a disqualification for being president for at least four years after the end of the senator's term (last term if term limits not added)