Well, we know that ash damages engines in subtle ways that can take a while to appear if you don't inspect immediately. The most recent thinking from the regulators looks to be that there are levels of contamination it's safe to fly through, levels that are risky and levels that are to be avoided at all costs... but as contamination is going to be cumulative, I don't quite follow that logic. Likewise, I'm not convinced by the "if you can't see it, it won't hurt you" thinking that some seem to have.; there have already been reports that the Mk 1 nose has detected conditions that the Mk 1 eyeball has not.
If we're going to be flying in any sort of ash cloud, I can't see an alternative to having quite sophisticated sensors that alert to conditions that require avoidance. They'll have to constantly check size, density and type of particulates, and relate that to a model of engine damage. That's not impossible: the sensor part may already exist, but probably not in a form suitable for widespread deployment.
Who's going do to this?