Part of me, jokingly (mostly), thinks we should replace it with a "carbon buy-back" program where people and/or the government can donate money to buy carbon from people and bury it deep or sink it in the ocean or something. Go clear cut all that land, sell it to the program, then replant. That's the only way I can see a market solution really working. Corporations donate to the fund to ease their corporate consciences and the carbon gets dumped down an old mine shaft and buried in concrete.
Of course, it likely wouldn't work for a lot of reasons, but it would at least be more on point. "Don't just promise to sequester carbon, bring it to us to dispose of" would at least help take the gaming out of that particular system.