There is a guy on Pinkbike selling a brand new, Medium sized, carbon, 27.5, Pivot LES frame for $1200. If it was a 29″ frame, I would have snapped it up already. You could probably build that up at 22 lbs pretty easily.
Why are you hung up on sticking with a 27.5 bike? I am the same height as you and recently moved to a 29er bike. There is almost no way in hell I am returning to a smaller wheel size bike now. There are several Santa Cruz Highballs sitting on eBay that would suit you. This one in particular. Put a short stem on it and it will be a party. However, my biggest recommendation for you at your size would be going with a lightweight wheelset. This will have a more pronounced effect for you over any other weight savings.