Maybe I'm misunderstanding what Fein is proposing, but I don't understand how this would be a solution to the issue of abuse of executive privilege. For what it's worth, I don't really think EP makes sense in a representative, constitutional government...but there are many who have very cogent arguments to defend it. So let's allow that since the idea is out there as legitimate, it would be hard to take it back.
And if you agree that EP should exist, why would the Executive submit to the decision of a panel of members from the legislative or judicial branches about whether the demands of those branches at large are "real" or "political voyeurism". From a purely theoretical standpoint, that doesn't even make sense. If information is supposed to stay privileged within the executive branch, then what difference does it make whether a small committee of congress-folk hear it as opposed to the entire legislative body? And to make the determination of whether the information truly should fall within the jurisdiction of Congressional oversight, I think that the committee would have to know what the information was...otherwise we'd pretty much be in the situation we already have. The President says that he'd have to reveal sensitive information to answer questions that many would agree Congress otherwise has a right to ask. And what's the point of EP if the executive doesn't have the ability to decide what information is privileged.
This of course brings me back to the notion that EP has no place in our government...because I'm a firm believer in the necessity of checks and balances within the Federal Gov't. Of course this would lead to a degree of inefficiency within the government, but if you're a US citizen that's what you sign up for. Dictatorships are certainly the most efficient way to run a nation...but I'm pretty sure that a lot of people sacrificed their lives a couple hundred years ago because they didn't favor that idea.