You'll need to be very specific about how these are flaws. What parts of the Articles indicate these? Or are things omitted that need to be there?
Whose unity (or lack of unity)?
Whose ambition? To do what?
Whose power (or lack of power)?
Whose liberty (or lack of liberty)?
You'll need to zero in on specifics in these terribly broad areas if you expect to find ideas in the Constitution that fix these flaws.
Did you read that second link I gave you? Ben's Guide... Be sure to read the whole thing.