I did that with a small Plains area, and I have very little issues. Not sure if night spawns are preventable when you are in the area though, and I get some overzealous visitors from surrounding areas.

In the Swamp, I've also had success with treehouses and raised catwalks between the trees, since mobs can't jump (they can walk stairs though, so don't connect to ground). But you have to like building, because that takes a while to be useful. And I learned that crypts are not load bearing, sadly.

Hope you find a solution that works for you!