In the last 2023 blocks, only 26 were orphaned. That's about 1,3% odds of loosing all the meltmined coins (to a lucky miner). I prefer a 1% chance of loosing the melted coins than your tainted coin system. Tainted coins will affect all the bitcoin economy badly but meltmining pools only have a 1% chance to loose the block. I insist, tainting coins is a very bad idea because it will hurt all the bitcoin economy and the solution is not so risky for a melting transaction.