I think you’ve answered your own question regarding the spec choices. If there’s that much you’d change (brakes and drivetrain) on the P7 anyway, it’ll be cheaper and easier just to build your own bike in the first place.
Me, I’d prefer a P7 (with Shimano kit), but that said if you’re buying a frame and building it up, the P7 frame is VERY expensive compard to the PA. We’re all different too, so what suits me won’t suit you necessarily!
Whatever you do though, you’re going to get a pretty good bike. Would err on the side of Rockshox forks, preferably with a 20mm axle, over anything from Fox though personally. Better damping, stiffer, more reliable (though heavier) IMO.