I'd say not to get a BTS, unless you have someone who can take care of it when you go away for the long weekend or on a vacation.

As far as snakes, BRB are wonderful, I'd get a male if I were you as the females will require a larger area. They require much higher humidity than the snakes you currently have though, so you'll likely need to add a moss flled box to provide a spot for it to go.

another option is move the corn up and leave the BP at the bottom. You've only had the corn for 2 years and the BP for less. Sometimes it's nice to enjoy them for a while before getting another. If you get a new one every year you'll quickly have 2 dozen - much less time on your hands, higher bills etc.