Where to start? We could broaden the base in thousands of ways. Here are two centrist tax raisers that are lots of people would agree to, and that are easy to understand. (Though not so easy to implement.)
First, we could stop letting multinational corporations make a mockery of the tax system. Take away U.S. corporations’ “deferral” incentive to operate abroad – and to their ability to claim that have more income came from abroad than they really do. And tighten our rules to hammer runaway (expatriating) corporations – past, present, and future. Or impose worldwide unitary taxation on all multinationals like may states did before the Federal Government stopped them. In any event, why give U.S. based multinationals a “repatriation holiday” for income they’ve already shifted and stashed offshore? Here’s a Humor piece from Tax Notes on the holiday: http://newtax.wordpress.com/wp-admin/post.php?post=1168&action=edit.
Second, we could tax the heck out of marijuana. An article from State Tax Notes on that topic is at http://newtax.files.wordpress.com/2011/01/8-june-2012-taxing-marijuana.pdf. This requires legalization, which is problematic, but if we the people of the United States of America don’t have the sense or the gumption to fix this, we can at least laugh at folks defending an indefensible position. You don’t need to watch the whole thing to get the idea: http://www.youtube.com/watch?v=kFgrB2Wmh5s
Centrist tax ideas don’t stop there. How about, for instance, indexing capital gains for inflation?