I've found this pic of a USMC AV-8B taking off and it would seem the jet blast from the rh wing tip RCS valve IS visable. However, the engine will be running at full power, and the pilot is taking off from a ship, which could be rolling from side to side itself.
I suppose it's possible that there could be visable jet blast, but in my picture maybe you see a little white triangle inboard of the wing tip? This is just the outline of the rear of the last pylon, meeting the wing tip. I also see a shiny white patch on the tarmac below it, but I think this is the white centre line on the runway.
Here is the pic of the wing tip again. Yes all of our Harriers that spent any time in Kandahar took a real beating. The low level flying through sandy air very quickly eroded leading edges and engine fan blades!!
I'm not sure what the little glass bubble is just in front of the light, I was a mechanical technicial, not electronic. The Zeus system allows the Harrier to change it's radar signal to that of a number of different things to confuse anyone tracking it. The rest is pretty simple.
I'm really looking forward to seeing your painting and your second Harrier. I only wish I had as much time to do all of my hobbies!!