Now you talk about a body that should be elected "by the states", the Supreme Court could be constituted as a body with rotating membership, with each state sending in one justice for one year as it's turn came up.
Now, should we then take a justice out and shoot him after his term is up? I don't know. Haven't thought that one through. Judges are a little different than Senators after all. They all wear the same color clothes to work for one thing.
I say why even have a Supreme Court? After all, NOTHING in the Constitution states that they will be the final interpreters of the Constitution; The SCOTUS gave themselves that right in Marbury v. Madison!
I say we have all Federal judges elected, with a state-appointed Senate being the final say.
Read Antifederalist papers no. 78 and 79 on this subject:
http://www.freerepublic.com/focus/f-news/1404661/posts