I can't believe that some people think that XTR is not capable of doing "longer slightly faster downhills"?!
As thisisnotaspoon says ^^ a lot of DHers use road rear mechs since they're lighter and have a slightly snappier spring action (also much shorter than MTB mechs so more ground clearance). You only have to watch that youtube video of trials on a road bike to realise that the bike will cope fine. You don't need specific "Alpine" gear for one week in Morzine per year!
Hell, I've seen guides in the Alps and Pyrenees on ti hardtails outriding guests, we got overtaken by some French locals on carbon XC hardtails (saddles up, stems down) on a descent in Luchon, even the guide on his "hardcore HT" couldn't stay with them.
Cast iron guarantee that the groupset will be more than capable of a week in the alps!