The Channel Islands?

[PBI]

Such islands would also be a lot more important if there was a limit to how far ships could go without resupplying (either from a friendly port or by simply stopping to chop down a few trees and refill sweet water supplies).

Would become a big consideration if steam ships make it into the game (a bit early I know, but could sneak in as a high end tech), since I believe this was essentially the reason Britain held the Falklands, and various other small islands, so that ships could refuel every few thousand miles rather than carrying enough coal to make the whole trip.

They were not populous, they were not strategically placed, they had no relevant resource, etc, etc, etc.

Unlike Rockall.