Re: tripod mounted rifle rest
I think you have a good enough of an idea to proceed to the next step. Build one and give it a go. It should be sturdy enough that your groups would be as good as you normally get from the bench to be effective at loooong range.
I'm working on a similar but different idea using a camera tripod but it appears that I don't have the metal working capability that you do. Go for it.
I may be the slowest guy on the mountain . . . . but . . . . I'm on the mountain!