In reply to Exile:
If you want something similar to the Mixmaster, then there's the Arcteryx Gamma MX pants, or alternatively use some like the Patagonia Super Guide or Mammut Base Jump pants with a merino/synthetic base layer. I have a pair of the Patagonia Speed Ascent pants (forerunner of the Mixmasters) and to be honest, they're fantastic for winter climbing, but way too warm for summer alpine use. You might be better off with the versatility of a 2 part system unless you want dedicated winter trousers.