We are members of a constitutional convention and must determine the kind of representative government to adopt, all tyrants have been overthrown or eliminated. Think about the political socialization aspects of the institutions you are advocating.
I would like to try a parliamentary system, as I think the government we have now becomes less and less representative all the time, and the two major parties have hammerlock on power which leaves many minority viewpoints completely ignored.
Our Senate and House have remained at 535 members for decades, yet our population now exceeds 310 million people, thus you have a system where people are less represented as each year passes. In a parliamentary system, government can change more quickly to respond to public desires, you are not necessarily locked into a set term of office (early elections can be called or coalitions can break apart) and because coalition-building is a necessity, minority populations and viewpoints have some chance at being a part of government.
I would argue for a constitutional system of government in which voters direclty elect representatives, and representatives collaborate to write the constitution. This is similar to how our constitution was formed. I think that the task would be easier in some ways, but also much harder in some ways. There are models now, but there is also a vast amount of information that was not there before. This makes the task much more complex.
I have to agree that I would be in favor of a Constitution much like the current one in the US. The Constitution has stood the test of time because it was well written, and done with forethought. The checks and balances of our system, as well as the Federalism set up in the Constitution keep power in balance. The Constitution is special because of its ability to be flexible as life in America changes. My only changes would be to make it easier and more likely for Americans to have direct votes on important issues. The electoral college is also outdated and superfluous. We need to allow Americans to vote the way they feel. If they do so in a uneducated way, so be it. I don't think we need politicians or electors to protect us from ourselves. We need to be able to vote directly for our representatives and have more direct influence (meaning more initiatives on the ballot) in policy making. If we mess it up, we'll learn won't we?
Personally, I would argue for a system very much like the one that is in place in the United States today. I sometimes think that a parliamentary system would be better, but I generally come back to liking our system with its possibility of divided government.
The great benefit of a parliamentary system is that one party is clearly in control. They can propose a platform and then go in (if elected) and implement their plans. They cannot be thwarted by some other party the way the Democrats were thwarted in their desire to pass their kind of a health care bill in the last Congress. This would make it easier to know what will happen if we vote a certain way and to know who is at fault if things go bad.
However, in the US, better results seem to come when there is divided government. The parties have to compromise with one another. When one party is in control, it tends to get "drunk" on its power and go too far one way or the other. Because of that, I think that I prefer a system where there are more checks and balances and there can be divided government which forces compromises.