Keep the hardtail if you’re going to get a 140-160mm bike, because (I hope, and I doubt I’m in the minority for saying this) a bike of that travel and nature is WELL over kill if you ride mainly trail centres. If I go to a trail centre, myself and anyone I am with are on 100mm hardtails, and it’s enough, having said that maybe a 120mm 29er full Sus would be quick.
I can’t help thinking that if you bought a 140-160 26er.. it would be great for the alps yes, but as your main and most costly bike, would you not rather have a bike that is fun and fast every weekend?
Get something like a 120 if you ride trail centres, even if you don’t like 29ers, get a 26er. Ride it all the time, have fun, be fast, then once a year a so if you go to the alps hire a big bike out there.