I think drop-in replacement fuel is the most realistic approach. The lifespan of aircraft and of some aircraft engines mean that your suggestion would require a

I think drop-in replacement fuel is the most realistic approach. The lifespan of aircraft and of some aircraft engines mean that your suggestion would require a large number of engine replacements and make it prohibitively expensive for the whole of GA. This approach clearly can work, and is only not working because of an incompetent administrator.