We don't need a new Constitution. The one we have isn't working only to the extent that the size and scope of the federal government is far larger than it should be. We need a new federal government. The Constitution is fine.
As for size and scope of the federal government, that's surely been decided by elected representatives according to the procedures of the constitution?
No, it wouldn't.
> The Constitution is largely very good, but it unintentionally created a de-facto two party system. With the executive branch free from that sort of nonsense, it may be that the legislature will right itself.
Not really; the EC isn't the key feature of the electoral system that produces a two party system, and the features that are -- the fact that most elections, and particularly those for the Congress, are by plurality or majority-runoff methods -- is nowhere in the Constitution, but is the product of statute (and, largely, state statutes.)
First, because its a lot easier to achieve politically, and second, because while I've got pretty clear ideas of both the legislative and executive approaches I think would be best, I don't think its a big enough change that there is plenty of reason to be cautious in imposing a uniform national mandatory rule.
I do think streamlining things would be nice. A large but simple government: everyone gets automatic healthcare coverage by right (like Medicare, but without age limits), everyone gets a basic income rather than some complex web of welfare, etc. Less bureaucracy and maybe even smaller government in terms of pages of regulation/etc., but larger "size" of government in the percent-of-GDP sense.
The American approach seems to prefer complex but low-benefit government, with huge piles of eligibility rules and private-sector provision, instead of just simple blanket benefits.