1) The Great Moghhul (The Dehli Sultanate) - In the North
2) The One or two members of the Maharata Confederation in the South - Historically the Confederation only co-operated against invaders from the North but if Agema is feeling kind it may give the whole confederation to one player.
3) The Shah of Persia
As well as the three commonly played positions there is also the The Afghans, Rajputs, Jats, The King of Kandy, Napal, Lahore and Gujerat.
Not Strong enough to unite India on their own but all possible problems for would be Rulers of India.
Basically in game terms its a bit like the Ottoman Empire having The Sultanate, Rumelia & Egypt positions any one of which can be used as a base to unite the rest. Or perhaps its more like the Holy Roman Empire with Austria, Prussia & Saxony-Poland (since like this last power most of Persia is off the map and has other concerns).
Also like trying to unite the HRE you have the problem of lots of small holdings by major European powers.
In terms of Agema challenges I would say trying to unite all India is more difficult than trying to unite the Ottoman Empire but easier than trying to unite the whole of the Holy Roman Empire.
Are you going to give it a try? In game its normally attempted from the Moghul position but Historically in our period the Maharatta came closest helped by a crushing defeat of the Moghul's at the hands of Nadir Shahs Persians. Then his Generals and Afghan allies came back to get the plunder they missed the first time and battered the Confederation.