Planewave too -
CDK700
The design is called Nasmyth or Nasmyth-Cassegrain.
For a dob you'd still have to worry about where the focuser would be. If it was OK near the zenith it would be too close to the ground for targets near the horizon. You'd have to move the altitude bearing a long way up to get the beam exiting through the bearing, and that would need a lot of weight added to the top to balance the scope.