Why bother with a ".308 Marlin?"
Either stick with the .308 Win, or offer barrels also in .300 Sav or .30-40Krag.
Actually, there'd probably be lots of folks who'd want the .30-40, even if they already have a .30-30, .308W and / or .30/06 - or all three!
..... Then, ..... if NEF offered the .30-40K, no doubt some shooters would insist on having ALL FOUR!
But again, why bother reinventing the wheel with a .308 Marlin? I'd take a .307 or .356 Winnie before choosing yet another new round. 