If you look at the history of the growth of the federal government it has never shrunk. It has a habit of always expanding, always encompassing, costing more, and on and on.
Your question is very good in that it asks what is out there that the FRA can regulate but have not. Unfortunately, I think that it is anything they want to. That is because of two things: First, no one really pays much attention to what the requirements of the constitution are and if they do, no one holds the government accountable. Government intrusiveness has become like algae. If not held in check it will invade wherever it can. The other thing is that even when the constitution is given lip service, the "interpretation" is so expansive that instead of being a limitation on government it is a license to to whatever it wants. The Commerce Clause of Article 1 section 8 which I mentioned earler is a great example. Instead of regulating commerce between states, it has been interpreted to be anything that "affects" interstate commerce. So, even though something like toilet paper would seem to be a particularly individual and localized use commodity, the fact that everyone uses it has a substantial impact on interestate commerce, and therefore subject to federal regulation.
I have practiced law for some 35 years. Half of that time was exclusively in the federal courts, up to the Supreme Court of the United States. If there is one thing I learned in all that time, it is that the Constitution is honored more in its breach than its observance. That is an unfortunate observation, but true. If there is any doubt just ask when was the last time the United States actually declared war like the Constitution requires? That is one of the most important and fundamental functions of government where the lives and treasure of our country are committed to a cause. While you're thinking about it, regardless of the merits of being there, how many of our brave soldiers have probably died today in the Iraq "war" and how much has it cost? So, what is a little detail like the Commerce clause to limit FRA jurisdiction. They will do whatever they want unless there is somebody out there to slow them down. Considering everything else, what are the chances of that?
Dan Markoff