If one based the battery on 06 length cases, the next would be the 30-06, then .338-06, .35 Whelen. After the Whelen one should probably think of using a different case for the basic cartridge. Maybe the new .357 Ruger. These would effectively overlap one another for the occasion where one needed a larger bore for the game encountered and still work wonders on smaller. If I were to reduce the quantity of bores needed for NA game, I'd go from .280 AI to the .338-06 and the .375 Ruger. The ballistics and power levels of the .280AI and 06 are so close as to almost be duplicates. The same with the .338-06 and Whelen. I'd go directly to the .35 Whelen if you dropped the .357 Ruger, 30-06, and .338-06. These rounds are effective on all NA game and would do for African plains game as well.