This series of topics has really been thrashed over the years. There is, I think, only one consistent reason for not trying to wash the ethanol out of fuel to be used in airplanes, and it's mentioned in only a few of the articles and posts. Ethanol is added to low-octane fuel stock for one reason: to raise the octane rating without using tetraethyl lead. When you take the ethanol out (assuming you do it properly, dispose of the waste properly, etc. etc.) you have lower octane fuel. If your engine is happy with 73 or 80 octane, "washed" autogas is probably okay. But if you are looking for 91/96, it's not likely that you'll be able to get it by washing even premium autogas.

(This is off topic and I will look for another thread to continue it, but my main concern is what modification is needed to make a regular aircraft engine work well on E85 or even E99. The FAA teardown report on the IO-360 they ran with AGE85 was not good news.)