I like this idea to.
If nothing else this thread does offer a lot of suggestions to HTC and lets them know many in the community would enjoy other icon options, especially special events.
This idea isn't to bad, I really like the scope of it. The halo especially helps against dark backrounds, and determins the airspace the aircraft is in. In addition to this, I'd like to see it also use the following:
The halo doesn't appear until you "aquire" visual of the bandit. At close distances, you only have to be looking at the aircraft for a split second or two before the halo appears, and it appears instantly. If you're at a much longer distance, say 6000K, then the halo would take many seconds to appear and could fade in/out depending on if you're looking at it or not.
So at long range you could see movement, keeping the A/C in your view, then the halo would fade in and identify it. Alternatively, if at long range, you might "accidentally" have an aircraft in your visual scope, but unless you're concentrating on the view, you might miss it entirely.
I feel it's about the best as it could get, with the limitations of the 3D vs. 2D argument.