Good gun choice. I would get stainless with a composite stock.
7mm is a very popular round I don't know where you got your info from about it not being common. Me I prefer a 280 which is just a necked down 7mm. Without all the recoil and has way better trajectory than a 270. But the 280 does not have many options in factory ammo.
I like your 7 mag idea maybe a 7mmwsm.

I also prefer Leopold optics they have the BBC ethical like Nikon. Either optic is good it's just a ford vs Chevy deal. Just do not cheap out if you are planning on 200+yds shots. Every scope I have is 3x9x40 and I am good to 350. I have never tried past that.