Hemu's ability to make his dynasty survive depends on more than just chasing out the Mughals though. In fact, I feel like the real challenge to the aspiring emperor will be peace and not war, because it's during peacetime that the Afghan lords are:
1. strongest.
2. least loyal to Hemu.
The Afghan and Turkish nobility were entrenched in India, and had been so since the foundation of the Delhi Sultanate. They had a state in Gujarat, for example.
They originally followed Hemu because he was a general of Sher Shah Suri, an Afghan who managed to usurp the Mughal empire and temporarily stop the erosion of Afghan privilege by the Timurid invaders. Hemu therefore received loyalty because he was acting on behalf of a Muslim Afghan.
Eventually, his army came to respect him on account of his good leadership, which gave him the confidence to displace the Sur dynasty (who had by now descended into infighting) and declare himself emperor.
So, let's say that he then goes on to win Second Panipat. Maybe he does it by not getting shot by an arrow during the battle. He'll then arrange a victory parade in the streets of Delhi, after which his feudal retainers go home.
The problem is, now those Afghan retainers
1. have no pressing need to be loyal-- war's over, and with it the unifying effect of being in an army.
2. are in their home territories again, where they can build up potentially rebellious forces.
So, any victory in war is going to be followed by another war-- a civil war -- where Hemu is mostly likely going to have the odds stacked against him.
A difficult premise, intriguing characters-- if someone does a TL of this, consider me subscribed
