an easy way to have a line freeze and turn the plane into a glider.

Then why don't cars have line freezing trouble with E-10 gas? Here in
Minnesota, gas line freezeups have essentially disappeared because of
the mandated E-10. It is the only good thing about gasahpol
though...........

I think a major reason not to use E-10 in certificated aircraft is the
~5% power reduction.