Having been in business for myself for over twenty years now (not in detailing) what you're doing is going to burn you out and cripple you before it makes you successful.
Doing things this way where it takes you far too much time to ever be profitable is not going to pay your bills.
And it's...
I feel like this would be one of those things that would be highly dependent on the vehicle in question and not something I'd particularly want to be the guinea pig for.
It's a clever use of physics but outside of doing an engine bay for a "dry" clean I don't see what the advantage is and I would think propelling miniscule bits of ice at very low temperature is more likely to harm paint than clean it.
But then again it's been over a decade since I saw the...