If you attempt an 'aggressive or creative' interpretation of the rest of the criminal law, you will very likely be going to jail. People have been trying innovative forms of theft for centuries, and the laws are broadly enough drafted that you're still going to be stuffed.

You're right about the high standard of proof required for tax cases, and the difficulties of prosecuting complex white collar frauds, but I'm not sure that we have to set the mens rea bat as high as we do. Plenty of other crimes can be prosecuted on "known or ought to have known" rather than having to prove intent.