two displayregions, correct fade between the two needed

Hello every body.
This is a bit unusal, I have a setup with a video projector.

The projector takes a 720p input,
The middle 5 vertical/horizontal degrees to be projected use 300x300 pixels, while the rest is stretched to a 200x100 degree area. Special lenses are used to achieve this.

Any ideas how a correct frame can be generated within Panda for such a bizzare setup.

My current idea is using

  1. Two display region
  2. one set to resolution of 320x320 but camera FOV angle just 5. Display region scaled to use actual 300x300 pixel area on the screen.
  3. second display region render at the high FOV angles
  4. second dsiplay region projected to a polygon with a premade vertices and UV map, to stretch the pixels from center to the edges, to essentially send a deformed frame to the deforming optics which will as a result un-deform it
  5. Have a grayscale mask to fade from the small middle 320x320 display region to the bigger one “under it”.
    Would like to know how to add a mask to a display region, or maybe I should render the smaller display region to a mesh as well (quad) and apply the mask as a textue to that mesh?

What do you guys think, am I missing something? Or is this doable? Is it okay to do it this way rather than shaders, or am I wasting my time making to slow of an application?