Been a minute since I’ve thought about that idea, but definitely a thing from the 1940’s w/ WWII era turbocharged engines using water/glycol to improve boost. But not externally. Mix was added to intake charge when you went to ‘War Emergency Power’ on the throttle, it applied the mix into the intake plenum, usually for only a few minutes in combat. @ Reno air races in the Unlimited class stars could push 150” of boost on built R/R Merlin’s using water-methanol injection, super hi octane fuel & special additives. Those mixes aren’t going onto the intercooler, it’s plumbed to cool the intake stream into the cylinders.
Your idea is real, Porsche 991 GT2 RS had sprayers out on the intercoolers. Diesel tractor-pull rigs are still using water-methanol to spray the external intercooler as to reduce charge air temps.
Just don’t think we’re at a point of needing to squeeze last bit of power out of a V35A, it has lots more. A external mix system would add complexity. Probably easier and cost effective to just put a tune on & fully use what you have installed.