I’m pretty sure a mass spectrometer will actually do what we want here, we don’t need a magic wand.

Drug dealers leaving solvents in because this suggestion makes no distinction between different cutting compounds? I propose that we do draw a distinction, then.

Drug users trying to hand us a baggie of their shit and call it heroin? I propose that, uh, we say no?

To be frank, none of your objections seem like very difficult obstacles to overcome.