1) The natural bridge is a safety zone for marine life. It is indeed heaven for marine life and carries Schedule I species i.e. Endangered Species listed under Indian Wildlife Act. You can not deny this scientific fact.
2) Remember Tsunami of 2004? The region has volcanoes and moving tectonic plates. The Ram Setu bridge is a barrier. Well, again I personally think that Shri Ram rescued many on the Kerela coast due to this "natural" (if you do not want to call it man-made or super natural made) bridge. You can not deny this scientific fact either.
3) While you consulted ASI, please do the honor to consult GSI(Geological Survey Of India) as well and seek their opinion on the issue. You must, if you are so inclined on this scientific reasoning to proceed with the project. Also, include Indian Rare Earths in your studies for a comprehensive view.
4) Segregation of duty conflict. Bloody Kaithiroli report, the only official study on the project done by Natl' Inst of Ocean Tech(NOIT) had Kaithiroli has it Director, who also happens to be on board of Dreding Corp of India for the Rs. 26000 crore project. Wow! Surely, the Kaithiroli report must be unbiased. Bullshit! Actually, the report claims that there are no rocks in Ram Setu, until a DVI dredger got it by one and broke its spud.
In short, this project to save 24 hours of journey ain't worth it. And have not yet mentioned the wrath of Hindus into the cost.