Is this an invention or does it exist already?

[pleuro3]

Sounds like a neat design. I would recommend using eggcrate (usually used as a guard/reflector fluorescent lighting fixtures in a commercial setting) for the plants to sit on. Its fairly cheap and completely inert. The big box hardware stores like Home Depot usually have it in stock. Good luck with your project and let us know how it turns out.

[JKeys]

Thanks, Pleuro!