I wonder if a simpler solution to all this regulartion would be something like imposing a tax (fee?) when larger companies acquire smaller companies? So something like, "For every order of magnitude difference between the acquirer and the aquiree, there will be a 100% tax on the acquisition price paid to the US Federal government."

So this would basically encourage companies to either have their own IPO (no fee at all) or be acquired (merged really) by a company of equivalent size. If you are acquired by a much larger company, that company will have to pay a (logarithmicaly) large fee relative to the acquisition price. If they really want it, no problem, but it will be "cheaper" for a more correctly sized company to acquire them.