It seems to me that there would, at least, be some sort of option to sign a release form that would excuse the insurance company of any liability on this issue. I plan on fixing the car in the near future, but I could imagine that car sitting there for an entire lifetime without anyone getting hurt, or there being any sort of problem. Anything could be considered a liability if one is willing to be creative enough.
As I said before (in a response that hasn't posted yet), if I were seeking to rent a home, and also owned a pet, I could find a landlord who allows pets. It's less common than the typical landlord, but such landlords do exist. If I could find a sub-community of home-insurance providers that would allow vehicles to be parked on the property, we could do business with them. Since the terms of any policy is merely a meeting of the minds between two parties, I have to believe they're out there. But where's the best place to find them? That's the million-dollar question.
I mean... there isn't really market for this kind of thing. Unfortunately, there is no answer to your million-dollar question. It's not a calculated risk, therefore, it's not of any insurable interest.
I sell through a variety of companies, a few being non-standard and I don't have any that would cover it.