Yes, its always important to limit those unsightly lines ;p
However, it is quite clear that there is very little you would need to add, and only a little you would need to change for a massive improvement in naval performance.
As to which ships, Galleon and Frigate level onward, POSSIBLY with the Portugese special ships getting it too (probably a good idea, since they were really booking it early on ;p)
I like the idea of the Guardsmen (how about Militia?) units being upgradeable to some other normal unit, but why not pikemen or crossbowmen, rather than something only slightly stronger.
I think Rhye already has done something like this with the resources, but on a larger scale: Americas with tobacco, Asia (China, Mongolia, Japan, India) with silks and spices, Europe with dyes or something I am sure, Middle East with incense.
The point is, this mod is not so different between civs that it really requires each of them to have a different resource. The current system is performing perfectly in that respect, at least in my opinion.
I am against a specifc civ being given a specific wonder simply because they built it in real life. Jeeping it in the right area, as Rhye did, is a splendid idea!
I know thats not exactly what you meant, but I think I am close.
Jeez, this is like framing a bloody constitution ;p
AND I ALSO THINK SEA LANES SHOULD BE ADDED! ;p