What's the benefit of "coin melting"?
If you just want to merge multiple "junk" inputs to one output, why do you add any tx fee at all?
I imagine you only use 'coin melting' if the accepted method of calculating which coins are 'tainted' only looks at inputs and outputs, and ignores transaction fees.
If coin melting ever becomes popular then it will stop being effective, as the taint calculations start taking it into account.