I was particularly interested in this quote:
There also is a problem in that rotors are by their nature two dimensional. This leaves two dimensions to which they would move the air. Only one of those two dimensions is up. The power used to thrust that air into the extra 4th dimension is wasted. It seems it would be necessary to enclose the rotor in a cylinder in order to favor the up- down direction.
Supposing that it is true that a rotor/propeller will indeed naturally expel fluid in a plane rather than confined to a line, there seem to be several ways to either exploit or avoid that.
In any case, propellers produce thrust perpendicular to their plane, and parallel to their axis. Thus, for an airplane, we want the propeller to spin in some plane perpendicular to the forward direction, and for a helicopter we want the rotor to spin in a plane perpendicular to the down direction. In 4 dimensions, we can do both of those things at the same time! Suppose that a propeller is spinning in the left-ana plane. it would then expel air in the forward-down plane--which means that, rather than fully enclosing the propeller in a duct to linearize the output, one could leave it open and obtain helicopter-like lifting force and plane-like propulsive force from a single propeller!
Alternately, one could more fully embrace the planar nature of the output, and replace the propeller with an impeller, which is designed specifically to expel fluid in its own plane of rotation, and would presumably be much more efficient at that than a propeller is. An impeller creates high pressure at its outer edges inside a casing, and tubes could be connect to that casing to direct pressurized air in desired directions. This a specific case of the more general idea of fluid jet propulsion, where the pump can be replaced with any other kind of pump in principle.
Finally, a variation on a cyclorotor should also work to produce one-dimensional thrust. A cyclorotor has blades mounted parallel to its axis of rotation, with continuously variable pitch (just like helicopter blades). To generate directional thrust, one simply ensures that the blades turn so that they are oriented flat-on to push against the air (or water, or whatever fluid you are traveling in) like an oar when at the point in their rotation that is tangent to the desired direction of thrust. And by altering the blade phase, one can get thrust in any direction in the plane of rotation. So, again, it would be possible to use a single rotor for both lift and thrust--but with more control than a partially-ducted propeller would have