The pork barrel members of Congress will never let it pass.
Just as important, it would throw a serious wrench into their behavior modification engine, whereby they pay us with our own money to do things we're not Constitutionally bound to do, and probably don't want to do anyway. (Think seat belt laws, helmet laws, limits on state DUI BAL levels, the requirement that the states even have a numerical BAL level, federal funding for schools, but with strings attached, etc.)
This practice needs to be stopped by whatever means are necessary or available. Nothing stops the citizens of the various localities from enacting those laws if they think those laws will benefit them. Why should it be any of the Fed's business?