We need 'Buffer States' between us (India) and China occupied Tibet. By maintaining this the land disputes will be between those countries and China only. Sikkim also functioned as a buffer state before it was merged with India.
India did plan to subvert Bhutan late last century utilising the same methods it did to take Sikkim by getting the Nepalis there to settle in numbers & outnumber the local population except the Bhutanese establishment saw thru it & expelled the Nepalis en masse.
That's one theory the other was the Bhutanese were being tremendously slack in expelling ULFA , Bodo & other militants sheltering there which is why the Indian establishment resorted to this ruse .
I'm veering around to the second explanation given the recent resurgence of calls by certain Nepali groups for reverting the state to a Hindu nation & revival of the monarchy given the massive inroads Maoists & communists have made within the body politic of Nepal & brought with it the baleful intervention of the Chinese with it .
Having said that under the current circumstances we need Nepal & Bhutan as a buffer . I'd argue for the same even if Tibet became an independent country with a closed economic bloc comprising exclusively of India Tibet Nepal & Bhutan with no visa required for travel as is the case today for travel between India & Nepal or Bhutan & ease of residence & work for its citizens in either country as it does exist today between India & Nepal .