Well, if you want to make it "smaller" without actually reducing the size, you could put up a bunch of barriers to keep players contained in a specific zone or to just reduce the amount of map they can play on. If you do that, try to add props to signify, so to speak, where the barriers are. My experience has told me that most players hate running into seemingly random invisible walls, usually because they don't understand their use, but still.
Orange means that they won't be able to pass through, and green means they will. Same thing applies to ai barriers as well.