Here's an unorthodox idea: The Mughals expand into the Steppe as well as India. They end up fighting with an alternate Russia and winning, triggering them seizing large chunks of Siberia. They probably won't be able to hold it together for long, but with a few lucky decades, they could probably get close to the Mongol Empire size.
It’s possible given a lot of luck, but before they get to Russia they’ll already be facing stiff competition from the Uzbeks. Up until Aurangzeb it was a standard part of Mughal foreign policy that eventually, they’ll get round to retaking their ancestral lands of mawara an nahr (Central Asia), Jahangir mentions it many times and the most famous serious attempt was Shah Jahans which ended up being a colossal money sink- he wasted more money there than Aurangzeb spent in his southern conquests and it didn’t result in a single territorial change. So don’t assume it’s for want if trying.
But yes if they did manage to conquer back their ancestral lands, the only thing stopping them from getting particularly far is the domestic situation- which to be fair would require an adroit politician to handle. Nevertheless, that too can be handled- perhaps the extra cash and presumably less money spent means that financing the southern conquests is easier/ the population isn’t taxed as much and there are fewer agrarian revolts. Or the image of a conqueror that the northern campaigns build up mean that the Deccan sultanates put up less of a fight, leaving more time to focus on dealing with the Marathas whether diplomatically or militarily.