It is a myth that "nobody knows" what the framers intended.
There are entire libraries of documents, meeting records, and letters that these people generated during the discussion of how our government was going to be organized. How they came to their conclusions and why, including knock-down arguments with other framers.
To hear some people talk nowadays you'd think somebody dropped the completed Constitution over a transom and hoped somebody could figure it out.
The "vagueness" of the Constitution is largely an invention of people who support an all-powerful centralized government, which is precisely what the Constitution, according to all those writings, was specifically engineered to prevent.