Yes - this has already been discussed.
No need for extra 'screens'.
Any one of several filters on turbine bleeds would do nicely.
See my previous posts here and especially over on the Engineers forum 'Ground Procedures for Ash'.
....but NOTHING will happen unless pressure is applied, decisions made, money spent and systems and procedures put in place! That's the danger of discussions such as this. Lots of suggestions but they eventually just slide beneath the waves unless someone, somewhere actually DOES something. (By the way, I have also made contact at CAA...we'll see...)