If I was doing one, I would build a 30-06. Since it is two, I would do a .270 and a 9.3x62. I certainly wouldn't do your 270/30-06 pairing because there is just too much overlap. With my plan, the guns could not be identical because the barrel contours would need to be different. But you would have the gamut from antelope/moose (in NA) and reedbuck/eland (in Africa) handled quite appropriately.
