I recently saw a Hindi film - 'Jodha Akbar'. Lavishly made historical film about Akbar's wife with Aishwarya Rai in the title role. I presume the movie was a success. If so, I think it is also possible to make such a movie about Ponniyin Selvan and make it a success.
Need to have a some star quality actors, crossing the Tamil Nadu border into Hindi terrory like Aishwarya. Maniratnam is well suited for such a film.