- Rewriting the Constitution in "modern legal language" to give much, much less room for the judicial "interpretation" that has rendered much of the Constitution invalidated (10th Amendment, anybody?)
- Getting rid of the previous judgments based on an extreme amount of mental gymnastics used to allow acts that were clearly unconstitutional- e.g. "The Switch in Time that Saved Nine" that allowed the Commerce Clause to be used as justification to allow regulation of almost everything*.
- Tightening up some of the loopholes in the Constitution that allowed for creeping government growth- there needs to be a balanced budget article in the Constitution, for example.
The basic framework set by the Founders was solid but 200+ years of many people with huge incentives of increasing their power and influence trying to get around it using any means possible has succeeded in gutting much of it that got in their way. Hitting a reset button would be the best thing that comes to my mind.
*Except to force people to not avoid participating in a market, that apparently is allowed under the 16th Amendment (see the Obamacare decision.)