Jammu and Kashmir is a multi ethnic state.
In
Kashmir valley there live the
dardic people, the
Kashmiris who are
muslims.
In
Ladakh there live the
Ladakh people who are
Sino Tibetan and are mainly
buddhists.
In
Jammu there live the
Dogras, who are some kind of
punjabi/mongolian mixture, who are mainly
hindus.
In my opinion Pakistan needs only the Kashmir valley because:
1. Kashmiris are dardic people and related to the dardic people of Pakistan (Shinas and Chitralis) and in extend also to Pashtuns (East-Iranian people).
2. Kashmiris always were part of Pakistan's predecessor states (like the Sikh empire, Durrani empire or Indus valley civilisation etc.)
3. Kashmiris are Muslims
In conclusion Kashmiris share ethnical, historical, religious and cultural ties with all Pakistanis.
Whereas Ladakh and Jammu people don't share these connections.
Only thing Ladakh could be relevant is the Indus river which flows through Ladakh to China.
So do we need whole IO Jammu and Kashmir or only the Kashmir valley?
Here is also a map displaying the kashmir valley: