Just came across a region might be of interest to u
Dolpo, in the far western corner of Nepal, just south to the border of Purang in Tibet.
Make sure to go to the upper Dolpo. This area maintains some of the most amazing and least visited ancient trading trails in the world, plus fabulous valleys and mountain passes(5k+ x 2), including one of the world's highest freshwater lake.
I've seen the pictures of the breath-taking trails several times before, without knowing which part of the himalaya range it belongs to. Now I know the answers given by a Nat Geo documentary "Crossing the Himalaya". This is also the place where the Oscar nominated film "Himalayas" was based.
Check it out for yourself