Closed cockpit would solve one problem and possibly cause another problem. I can imagine unusual circumstances where a closed cockpit would impede getting somebody out of an upside down burning car (for example).
I think the discussion of closed cockpits was inevitable in this thread but in an attempt to separate it from a thread meant to respectfully inform about Wilson's passing I've started a dedicated thread: http://www.motoringalliance.com/forums/off-topic-racing/25781-closed-cockpits-open-wheeled-race-cars.html#post338100
An excellent farewell write-up by Marshall Pruett here: Indycar Racing News | Racer.com - PRUETT: Befriending the Badass –Â*Justin Wilson