I talked to a retired friend of mine who was a chemical engineer for Dow (an avid MXr who used to ride with Dick Mann back in the day). I asked him about E10 and showed him the pics of your throttle bodies; he said that ethanol is a solvent and by itself wouldn't leave those deposits. He said that crap looks like old gas varnish from the fuel system (tank, gas lines & fuel pump) that was dissolved by the ethanol and got deposited on the butterflies where it accumulated and hardened.
I asked about the corrosive effects on aluminum engine parts and damaging the brass injectors, he said aluminum would be affected if it came in direct contact with ethanol, but at the 10% to possible 15% found in gas it would be negligible. He said it would have an even lesser affect on brass. He said it will eventually dissolve most if not all rubber gaskets, and it will dissolve the resins in fiberglass and epoxy.
I know ethanol BTUs are lower than gasoline, so performance is definitely an issue, but after talking to him I get the feeling that understanding how to cope with ethanol is the answer. He said ethanol additives simply bond to the ethanol molecules to help mitigate water absorption, so that is a line of defense, but he said that might adversely affect fuel economy too.
I don't think we're going back to ethanol-free gas anytime soon (in Calif). I still think your fuel cross-over drain is good idea, especially for ADV riders who attempt
Although he and I both agree utilizing food grains to produce fuel is probably not in the public's best interest (but a money maker for someone).
Anyway, my 2¢