No there is only one value that you can change, it governs the number of action (movment) points all classes get at the start of a turn. So if you were increase it, all classes (ie agents, FM's, admirals) would get a movement increase;.

A possible way to give just navies a movement increase would be to play around with the trait files to give all admirals a trait that increases movement speed but I'm not too knowledgable when it comes to that area.