I just got my Dragon copy today and was looking at it during lunch, and I noticed the same thing about the stables and ramp.
I decided that if I used this keep, I'd move the stable to the ground floor and make the ramp exit outside, and make the first floor the second floor with a narrow ramp or set of stair leading up to the main entrance. It would be easier to defend that way, too.
Oh, and I'd move the trap door going to the roof to the other side so it would line up with the common room/open space on the floor with the main bedrooms. That way the trap door wouldn't open into the master bedroom.