A SAUM would require that he alter bolt face, but OK. Great cartridge. Actually, the Weather 6.5 RPM looks like it has great promise and it retains a .473 bolt face. Basically a stretched .284 case.
I don't know enough about his hunting situation, so he may may not need lots of HP. all of these rounds work with a good bullet and a good eye.
The 6.5 Weatherby is one I've forgotten about. Of course, they don't have the advertising budget to get a bunch of 'sponsors' to hype the heck out of it. Ruger, Nosler, ... how many more variations do we really need to duplicate what we basically already have?
Hmm ... how much to create the 6.5SP with an ad budget to beat all the others in the marketplace and get it past the wildcat status?