Michael Vick
#1
So one needs 5 cities to get 6 resources. Sorry, but who in hi right mind would build that. There shouldn't be more than one city per Island group that is capable of getting all (or almost) the resources.
The Azores are two cities to get 4 resources.
The Madeiras are 1 city to get 3 resources.
The Canaries are two cities to get 5/6 resources and and optional extra city to get two, which will probably never happen, because Spain is already loaded with salt.
Sugar and bananas aren't found anywhere else in Europe. 4 cities to have a monopoly on those resources until colonies come around? I, in my hi right mind would do that.

Plus for Portugal it's required to build there, might as well have options, no? (There isn't even any salt in Portugal, another perk) Again, you don't have to build all the cities, it's up to the civ.
@SF23, It's not ocean, it's just the effect of when you change a previously land tile to water.