Well basically that would be it but it won't have to check much, only check if you're inside a house map and then send all spawns of the players inside the pool you are in.
I am not sure that would be a drawback in performance, and oh...I didn't know that it could be more than 5, at that point it would be a little more complex, yet making a dynamic map system like saving a file for every character that owns a map will probably get some time to think about it when you don't know where to start. At least this way I got an idea where and how to start. Making a map a duplicate of another under a different name doesn't sound too easy and more complex than my idea.
I am not sure that would be a drawback in performance, and oh...I didn't know that it could be more than 5, at that point it would be a little more complex, yet making a dynamic map system like saving a file for every character that owns a map will probably get some time to think about it when you don't know where to start. At least this way I got an idea where and how to start. Making a map a duplicate of another under a different name doesn't sound too easy and more complex than my idea.