Boy would I love a movie on the Battle of Leyte (and maybe the larger Battle of Samar). That battle within the battle was, in IMHO, the Navy's finest moment. The little ships taking on the best of the Japanese Navy, winning against all odds. The mice roared and fought like lions and they won day.
Tom Hanks is a more laid back type. It might be his comedy background showing through.
Gibson has the intensity needed to portray a good battle epic.
I would suggest using unknown actors like they did in Band of Brothers, that way they could be directed by him to give some unforgettable scenes.
Use good acting and direction, aided by select CGI, and a great movie could be made fairly cheaply.