Giro Pneumo is my helmet of choice. The reason is the comfort. It is very light, and at speed is pretty quiet. I also like the ROC4 that secures the helmet to the head, making the chinstrap not the most important part of the helmet. I have an old Giro Ventoux that was totally held on by the chinstrap.

Redesign? Aero to make the helmets quieter at speed..less whistling
Weight..light but can they be stronger?
Does any other material work better than polystyrene on the inside protective portion?
The ROC4 type system that everyone has...the best one I've seen is Limar's on the F111..it's a strap that's padded rather than a plastic structure...can that be improved for comfort? And secured to the helmet better than a snap/clip type of approach?

Brussels eh? I used to live in Waterloo...my Dad used to work on Avenue Louise in Brussels. I took full advantage of Belgian bike rides doing the famous parts of Liege-Bastogne-Liege, Tour of Flanders, Gent-Wevelgem...cycling history.