I actually started writing up a a new constitution a while ago as a sort of thought experiment. It's not finished yet but some of the highlights thus far include:
- A unicameral congress, with uncapped membership
- A right to privacy, free education, internet, and government transparency
- Freedom from religion clauses
- Constitutionally limited intellectual property: Copyright is 15 years for corporations, life for individuals.
- Uncapped supreme court, 2 appointments per presidential term
- Score voting for the president
- Proportional representation for congress
- No term limits