Unfortunately, that mechanic seems deliberate. Fill up your space so you'll have to buy the new islands. I like the archipelago, but I've yet to touch the rest. Every other building can be unlocked or upgraded, but these buildings just take up space and get tucked in a corner as far out of the way as possible. Since they share a cooldown, any more than one is otherwise useless. The only one I could see being useful is the Christmas market. With 4 of them, you could have two sets of market areas running on alternate times.
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