The question of HH Dalai Lama's Presidency of India should not be seen in isolation. The premise of this thread is that it would strengthen Indian security and territorial integrity, if Tibet is officially merged into India through an Instrument of Accession, approved by the Tibetan exiles, Tibetan Parliament and HH DL.LoL......it is not question of worth the trouble. It is the question, of if he is the right horse to bet.
If such a project is undertaken, only then HH DL's candidature for Presidency of India makes sense, and its success is to a large extent contingent on his being made the President.
Now no Indian whosoever can contribute anything at all to the success of such an undertaking by becoming India's President, and no (currently) Tibetan other than HH Dalai Lama can contribute so much to its success either, which makes current HH DL Tenzin Gyatso's position unique, simply because he is the HH Dalai Lama.
So even if he was the most vile creature on earth and it was considered in India's national interest to ensure the success of this undertaking, he should be made President. The offer would have to go to him, regardless of his virtues and achievements.
In that way, the question you pose, whether he is the right horse to bet on, is irrelevant because he is the only horse available (as far as I can see).
The right question would be whether the pro-forma Merger of Tibet into India is a sensible thing to do, an issue which we can debate. Of course you can agree with such a merger and still claim one should choose a different President, but then you would have to tell which other person would be more useful than the HH DL and why.