Still no. If I've got the sort of idea which can be proved with a cheap and quick MVP, then pursuing that is obviously better than paying a one-time "idea valid

Still no. If I've got the sort of idea which can be proved with a cheap and quick MVP, then pursuing that is obviously better than paying a one-time "idea validation" fee, and it won't take months. If I can't figure out how to put together an MVP, then I'm looking at a different style of business where I want people with the sort of knowledge you're talking about either in the company or in my social circle, and a one-time consultation wouldn't be nearly enough. Something to bear in mind is that an idea on its own is fundamentally worthless. A report of the type you're talking about would not add value in the way an MVP would.