We will have to hold Lhasa and a few other choke points and then basically connect 20-50km of road to the existing colonial chinese infrastructure in Tibet.
Well, there is a problem: Every year, there are always several months, the transportation in border area will be blocked by snow. Certainly you can support a small group of soldiers by air-drop but for a dozens of divisions, it is impossible.
The logistics supply line from our heartland to Tibet frontier we will make is shorter than from Chinese heartland to indo-tibetan frontier.
When you start to match deeply into Tibet, you are moving far away from your heartland and you are shortening Chinese supply line.
And if China is busy in a war elsewhere, we will have sufficient time to build the required connections and hold tibet, particularly since the local population will be more friendly to us than they are to the Chinese.
Firstly, if India decides to capture Tibet, that will be a full scale war, India will have to prepare it for a very long time. Since it will includes massive forces deployment, economic adjustment and material accumulation, there is no way to hide that from Chinese eyes. If Chinese notice India's preparation, what will they do? Continuing their preparation of the war around Taiwan by ignoring you, or shift their focus to you?
Secondly, the local population may not like Chinese, but it is not necessary that they will be friendly towards Indians either. Today's Tibet is no longer the Tibet 70 years ago, it relies on the food, energy and resources supplied from the rest of China. Once Chinese withdraw, India has to fill the gap by supplying resource, equipment and technicians. That is not easy job for any country (it took Chinese 70 years to build such a system). If you can't satisfy their demand in very short of time, what will they do? It is just like Nazi army in 1941, they were welcomed by Ukraine people as liberator in the beginning, but soon became the hated target. Why? They simply couldn't re-organize the local social system after Soviet pull out. You may think you can rely on Dalai Lama, but come on, they already left there for 70 years.