Are being in the mansions more important or being close to the main building/pool? Of course, preferred rooms are closest to the main building/pool so you may not end up as close to them as you want.
If being in the mansions is most important, I would just request Magnolia Bend and leave it at that. The mansions have half the standard room inventory they once did with the addition of the Royal Rooms taking over two of the four mansion buildings. And FWIW, if you do get in Magnolia Bend, you will be in Magnolia Terrace or Acadian House - both of which are equal distance to the main pool and main building, and not a far walk. Just across the bridge to the pool and across the bridge and around the path to the main building.