The Chinese reject visa applicants who indicate they will enter this province, so the itinerary you submit to get your visa will have to be creative
What do you suggest then? If the plan is to enter the Xinjiang province, that is what he has to put in the application. Anything else would be lying to the officials, which I assume would be illegal.
And what do you mean by "take care how you word your application" for Pakistani visa?
What is not doable on your itinerary is Borneo, travelling from Sabah to Brunei to Sarawak. Look into it and you will see what I mean. I would choose 2 weeks in Sabah or Sarawak only. The only reason I would consider Brunei on a short itinerary like this is to tick off a country to say you have been there.
The other part I think you won't be able to do in 3 weeks is the Azerbaijan/Georgia/Armenia leg. To tight if most days wasted on public transport.