OK, so I get there would be an "improvement" over the 7.62mm. But if I were going to do that, why not just bump it to a .35 Whelen? I mean, if I were filling out a battery, I'd probably go .25-06, then .30-06, then .35 Whelen. That covers North America. Bigger than that, .375 H&H.
I mean, it's not like the 8mm is going to kill a white tail "more dead" than the 7.62. If there's something the .30-06 would be marginal on, I'd want to step it up a bit more than 8mm. But that's just me.
I guess it does make sense that I could convert a 8X57 Mauser. Easier to re-ream the chamber than to re-barrel.