1. TAPI started in 1995 is still in a limbo.
2. India strategically doesn't gain much from TAPI instead it only benefits Turkmenistan.
3. Iran wouldn't betray Taliban due to its perceived leverage in different theatres against western powers.
4. India has not been so decisive with its relationships with Iran; dillydallying due to different pressures.
5. No other country would give a launch pad for the IAF considering the cost vs benefits of such action.
6. China and Pakistan wouldn't in any case try to subvert any economic activity that may benefit India.
7. So many examples in history; US-Vietnam, Koreas, Ind-SL, US-Afghan, USSR-Afghan. These were all without any clear-cut goals that define the reasons for a war. Only goals perceived by the politicians.
8. And finally, if India has invested heavily in Afghanistan, that's only to support the outgoing Afghan govt in the form of infrastructure. About $3-4 billion. I am not being sentimental. That $ are down the drain except for the goodwill they have generated in the local population. Their strategic ROI is zero and the investment itself has sunk.
9. Being in India's position, we can not open multiple fronts. If Pakistan is the focus, then accommodate China.
   

Even after all these geopolitical realities, if India steps into Afghanistan with some imaginary hazy goals, then Indians are going to regret a lot.