So, I CAN build it and if Sims want to go there for a visit they can, right? I just can't save it to library and place it down even if it's my own build? Like they can go to a park I've added to or remodeled, (following the rules for such), and no one has to "own" it.
What brought this to mind was I recently had my family visit Sulani and they had a great time fishing, becoming mermaids, (well, some of them, not my founder), and I kind of wished they could stay for a bit without having to do the unforgivable act of moving there. They can call in a vacation day, or simply go to work from there, and revisit or be called back to the place by someone already there. They wouldn't actually be able to "call up" a vacation stay like in Salvadorada or the mountains but with a little imagination they can have fun and still skill up there.
One of the reasons I had my "helpers" become mermaids is they are elderly and really falling apart. Every day they are too exhausted to do much of anything. I thought, great way to test out mermaid. Does it make them younger? No! But it does give them more strength and enables them to exercise more safely, and the mermaid charms are wonderful for fishing skill! (No more, X is dangerously tired notes!) I'm pushing it and having one of them deep sea dive repeatedly. I figure if they get worn out they can rest in the ocean and recover.