I just figured it out. I'm a genius!
So P5's have a second pump for the rear window washer fluid, but it draws from the same reservoir. On the P5 stalk, there is a way to activate the rear washer without turning on the wiper itself. If you turn it up instead of dow, you will get washer fluid and wiper on the rear, but this one position of "fluid only" seemed pointless to me - until now. You can run the rear window fluid and the front fluid at the same time since they have seperate pumps, which is why this is such a sweet idea. So, buy yourself a P5 washer reservoir, the P5 wiper stalk (it will plug right in) and the P5 rear washer pump. Now, hook your IC sprayers to the rear washer pump, and voila.
When you pull back on the stalk (just like now) you will get washy on your windshield. Turn the stalk, and you will get intercooler sprayer. Wanna wash your windshield and spray the IC at the same time? No problem!
I'm gonan do this with my car, but still install diverters because I still have a rear window that I'd liek to wash once in awhile.