I think you're best bet would be to use the Mauryans and just have them recieve scripted reinforcements if certain conditions are met, to represent reinforcements from the east.

You could also increase the Indian provinces trade bonuses even further to represent trade with the east (this has already been done in EB1, but I thought that an even larger increase may do well to represent the trade of a contiguous empire).

Choosing a capital might be challenging though, as the Mauryans real capital is east of the map edge.

Bootsiuv