"I've asked a couple times if anyone has seen a shareholder rights plan that enables existing shareholders the right to participate in future PP's in the same % as their original holdings regardless of the stupid accredited investor rules. Anyone?"
Often discussed and wished for, but I've never seen it. The guys that get those kind of non-dilution rights are big players, venture capitalist types that fund a company before they go public, or participate in PP's afterward. They have bargaining power.
Don't forget, often a stock price will go down on a PP, so one might be able to keep their percentage interest level in the company by just buying a proportionate share a couple of days after the PP.
And if the additional stock is sold publically, you might be able to get a piece and if not, again, you might be able to do almost as well if not better than those who do participate by wating a couple of days then buying.