My first idea was re-routing the rear screen washer pipe to the intercooler with a little nozzle to mist the water so you could spray it off the stalk (stealth sprayer). I can see two problems with this set up. You either spray windscreen washer fluid on the intercooler or run water during the summer months and just don't use the sprayer in winter when the bottle is full of washer fluid.
The other problem would be the rear wiper flapping away when you're spraying.
I then found a windscreen washer kit (bottle, pump, wiring, pipe and switch) for £11 on eBay so you could just fit that and have a button/switch you could engage for that extra powah!!
Anyone tried anything like this before?