Cylinders would need to be redesigned to handle 12.5/1 ratios the highest generaly used with aero piston engines today is 9/1.
An alternative to 100LL is being developed and tested now, with good results....so far, and, this alternative will require minimal engine mods, in many cases, except a changed mixture (easily accomplished).
FADAC has been certified on some TCM Continental engines as well.
In addition, direct fuel injection has been used for at least fifty years on many spark ignition aero engines.
Nothing new, either