Or expensive technology. I can’t imagine that they can’t get treated glass for the windows at this time. There are a lot of people working on new materials. Engines probably the biggest problem. Volcanic ash gets hot in engines and melts - adding a coating of molten glass (from what I hear). Non stick coating on jet engine parts so the glass does not stick to the jet engine. Perhaps a vent somewhere, so the molten glass does not accumulate in the engine, but is removed to where it can be removed easier. Perhaps a molten glass trap. People have mentioned air filters before. It’s been said that wouldn’t work. So, a better air filter.
A lot of good ideas in your post. We’ll see if the aircraft manufacturers begin addressing this problem with better technology.
For the time being, I suppose the aviation industry will just react accordingly to conditions as they arise.