Having grills manually put on is something that would get forgotten or left out - people rush and take shortcuts, thats human nature and unfortunatly leads to tragic incidents.
I never thought of the icing problem with the grills - maybe if they were retractable somehow so that they would be deployed only
when required.
Umm have a few ideas of how that could be done... maybe I should be going to the patent office rather than sharing my ideas here....hehe
G.