An oven using electric heating elements creates zones that widely differ in temperature, depending on proximity to the red hot heating element.

 

Some modern units with a fan for circulation of hot air inside, should be considerably better. Microwave ovens deflect radiation into all directions with rotary motion. Can some type of moving 'mirrors' be implemented to incandescent heating elements to spread the radiated heat evenly without air currents ?

A reflector will do that. I think infrared rays obey the laws of reflection. But, a good deal of the energy will be absorbed, making the system less efficient. Further, if the specific heat capacity of the reflector is high, it will absorb a significant heat without appreciable risk in temperature.

Also, microwave deflection is a somewhat different circumstance because it's not a thermal system, while heaters are. So a heater system can only have the oven get up to the temperature of the heater, owing to the 2nd law of thermodynamics (there's no work being done). Generally you will have a temperature gradient in the oven, as whatever you're heating up will have the lowest temperature, and you can't do anything about that.

 

But microwaves can be redirected (and theoretically focused) and make the target very hot, since the system is doing thermodynamic work rather than transferring heat.

The traditional approach is to put a copper box in the oven, spaced away from all the walls + the floor.

 

Inside the box, the temperature will be very much more even than outside it.

For cooking something where I want a more even heat I keep a large flat pan on the lower rack. It essentially absorbs and reradiates the heat more evenly. Other than getting the pan up to temperature there is no significant loss in efficiency that I can think of.