On our last trip my daughter chose staying at SAB over going to the water parks several times. I understand the water parks are more exciting than the hotel pools, but there is something relaxing about a day at SAB. I do worry that if it rains, or worse if there are thunderstorms, you will not get the added fun you envision.
I think one night is doable if you keep your suitcases pretty much packed.
For me, I would consider how easy it is for my family to pick up and move, whether I would be okay if the weather doesn't cooperate (there is still a lot to do within walking distance of the resort), and perhaps most importantly whether the pool would offer a family experience not better served by BB or TL.
DD11 like water parks, but mostly enjoys swimming and playing in the sand. It's a great place for her now, but she may change her mind as she gets older. If you are expecting a water park type experience, it might not live up to your expectations. If you are expecting a resort pool with more variety it might just be a great ending to your vacation. BTW, although my daughter liked SAB more than the Volcano Pool, she liked the slide better at the Volcano pool.
All that being said, I wouldn't suggest it unless you plan on utilizing the other advantages of staying at the BC (Epcot, HS, dinner at one of the area restaurants). I love the short walk to Epcot almost as much as the boat ride to MK from the Poly. Sadly, I will miss the boat ride this summer because we are doing a AKL/BC split.