Window box for cats

I want a window box for our two cats.

I was thinking about building one myself, but like all my other projects, it would likely take me forever and a day to get it done. Whereas if I could find someone to build it for me, it might actually get built in a timely fashion.

I am thinking:
* a solid platform, perhaps two feet by three feet
* Plexiglas, sloping roof
* window screen sides
* removable Plexiglas back, where it opens into the house, with a built in swinging cat door
* easy to install and remove in an existing double hung window

There is a second part to this idea. I looked on the internet for something like this, but I could not find it. I found some similar items, but they were all rather small and flimsy looking, and certainly not big enough for two cats. If this thing could be designed to be easily assembled, then it could be shipped relatively cheaply in a flat package. Which means they could be sold nationwide, via the internet or pet shops or whatever. Such a design may take more work, in which case we may have to build more than one. A prototype to try out our ideas, and then a second one to sell.

If I could line up all the necessary players (manufacturing, advertising, billing and shipping), it might make a worthwhile business.