As I read it ethanol's problems are with the fuel systems, not the engine, because it can damage plastics including fibreglass. It is also hydroscopic and the absorbed water can cause problems in the injectors. Given a little notice car manufacturers can easily use safe materials. Modern car fuel systems are not open the the atmosphere so water absorbtion is not a problem. It may be around service stations though because water does [or at least used to] collect in u/g tanks. 10% blend would be the highest reasonably doable for at least a decade.
