One possible solution is to replace the (1920 tech) magnetos with an electronic ignition system that adjust timing in function of power required, fuel qualities etc.
Such a system is under development and is in the certification process. It will allow a lot of high power engines (IO550 etc) to run on MOGAS or 82UL without any power loss.
The designer says that the price will not be any higher than current magnetos (over the lifetime of the engine).
Have a look at the website
www.gami.com