The problem is though your hypothetical is based on rational thoughts of rational people... which to a great extent the Indian people are not or at least the rational voices are drowned in a pool of irrationality...
Further, I think you are missing something from your analysis of ‘Indian delusion of being invaded by China’...
1, we have examine how India treats its own ethnic/religious minorities, which for the most part are oppressed by the majority. We have even seen suggestions from Indian think tanks that they should be eliminated out right.
2, Indian media brainwashes their people into thinking that China will invade and oppress others... the example given are Tibet and Xinjiang while conveniently omitting that China PRC had every right to reclaim Qing and ROC territories... other examples include but not limited to SCS, Pakistan (debt trap), Sri Lanka (debt trap) and Africa etc...
3, Indians have a history of projection... what they themselves want to do to others they will project onto the other... it is obvious how India conducts itself to its other immediate neighbours that India desires to expand its borders or make vassals of other states, should they be able to take control of other states they will probably cleanse the area... much like what they are doing in Kashmir with majority support of the Indian people too... so you can see what they will likely do should they take control of Chinese territory and in-turn they also project this onto the Chinese, along with point 2, the average Indians likely believe that the Chinese have the desire to take control of India and they will simply massacre the Indians and take the land...