I know about the problem to put a Safari barrel set into the standard Blaser S2.
What I'm trying right now is to get my Blaser dealer to order me a Blaser S2 Safari in 9,3x74R - costly as it will be - about Euro +1000 compared to the standard S2 in smaller caliber - this will give me all options for the future. I also prefer the classic straight stock withe the round cheek-piece over the bavarian style stock.
Not sure what I'll get: 500NE or 500/416NE - the barrels for the 500/416 could be really heavy, don't know yet. This way I can try the rifle for a year or so and decide if I would use it in Africa and what the barrel set will suit me best.