LOL -- Lisa, you've definitely got the right idea there
Personally bud, I'd start researching some arboreal snakes, and pick one that was suitable to your tastes, and go get one... hehe... A new tank just calls for a new animal
The rat or the boa might use the height a little bit, but I think that an actual arboreal snake is in order here
In general, it's not really recommended to keep any snakes together... however, you probably could -- just remember to feed them separately (put each one in a separate container at feeding time). For the ratsnakes, I'm not sure -- I know that kingsnakes can be cannibalistic, and ratsnakes are part of the same family... I'd do a bit more research on that one. I think that you'd probably be safe with the boas, but I'm definitely not an expert....