Diesel aircraft engines are not all they’re cracked up to be.
And replacement aircraft engines of modern design suitable to modern fuels would be far cheaper if they were sold in their thousands, rather than the drip-feed of today.
So perhaps what is really missing isn’t a drop-in fuel replacement, but a drop-in engine replacement!
But of course, there are many that believe we will still be running O-540s 200 years from now…