Interesting stuff here. Let me echo the sentiment regarding taking care not to burn your house down, and add "don't electrocute yourself". I've seen a lot of amazing home-built projects for vacuum forming and the like, and this will likely have some similar requirements. If you want to actually build your own custom heating elements, a search for those projects will likely yield some valuable information regarding formulas for coil length, and sources of materials for heat management, etc. Also keep in mind that you'll need close to 400 degrees F, which may be hard to achieve in a large area without at least 220v driving the coil. This is why countertop ovens, running on standard 110v power, are never very large. You may be able to do it in a smaller area with direct radiant heaters, an appropriate distance from the part. The quality of the result is going to depend greatly on the uniformity and control of the heat.
I'm not sure if you have had any exposure to the powder coating process, but it's messy and the materials can be costly. The good part is that they can be re-used, if you can keep what doesn't hit the part clean, and fashion something to collect it. I also recommend good ventilation. The powder is fine and will go where you don't want it and as the process involves heat to melt the powder, there is going to be outgassing and possibly odors your family members may find objectionable.
Good luck, and it will be interesting to see what you come up with.