What is about implementing coronas effect? I have seen something like that in legacy sourceport, looks very nice. Coronas are to be rendered like hud effects - if corona lighting source is visible, then corona is visible too, and it overlays anything, so i think that must be a hud effect. more - coronas are never scaled, they are of the same size on the screen independently of distance to corona source. but they become more translucent when this distance grows up.
I know my english is bad, so i add a screen from legacy =)
If it is to be implemented i think coronas may be defined in fxdefs, something like lighting: colour and size.