Ah, the table has definitely helped clear things up for me. Obviously this is one of those things that will require a lot of gameplay testing as well but right now it looks like it's a serious improvement on the current state of the Navy in CiV.
To make Marines have that edge over Submarines, maybe they could have a strength bonus against cities? It would be really cool to have a dedicated naval city assault unit in lategame - scout out with the destroyers, sink any boats that are protecting the coast with subs, bring in the battleships to soften the city, and get the marines to finish them off. I'm getting excited about this just thinking about it, and I have never been remotely interested in naval battle in CiV before!
That being said, the example scenario will never happen, because the core problem with the Navy in the game has been the AI's absolute lack of any basic knowledge of what to do. I am yet to ever have any opposition to an invasion over an ocean, all I've had to do is have a handful of battleships to bombard the opposition. Hopefully Firaxis focuses on this when designing the new naval features in G&K.