I'm not planning on installing a body kit on my car, but I expect you shouldn't have much trouble finding ten people for something like this. A few comments though since you asked:
1. From the pictures, it appears the radiator exit is much larger than stock, makes me wonder if the 300RR uses a larger radiator (I expect so). If you go forward with this kit, you might want to be sure that the radiator exit is properly sized for the stock radiator instead of just copying what you can see in the pictures.
2. Also at the front clamshell, you might want to ensure the access panels aft of the radiator are still removable and not integrated into a single piece front clamshell. If you could use the stock access panels, even better.
3. As someone pointed out in that other thread, the side skirts are not an easily reversible swap - the stock ones are glued in place, so it'd be tough (impossible?) to swap them back for these parts later. You could always look into *covering* the existing side skirts with this new one...that's what was done with an MR2 body kit I bought way back when (Aeroware), looked great but reversible. The challenge with the Elise/Exige, though, is the side scoop, how to enlarge that without removing the stock one (in the MR2's case, that body part was easily removable so was just replaced with the body kit one).
4. When working with that body kits company, be sure it's very, very clear what specification the prototype is to be made to, you don't want confusion. Make it clear what should be the same, what should be different and how.
5. The lower front end has recessed areas just ahead of each wheel...while I'm sure these are functionally good, I think they look a little weird, you might want to consider making the kits with a smoother front end because, let's face it, few or none of the potential buyers truly need optimal aerodynamics, they'd be buying the kit for its looks (and it does look nice, no argument there!).
6. Have you thought about looking around for a different company to partner with, one that wouldn't require deposits up front but is willing to take a risk? Or teaming up with one of the Lotus aftermarket companies, get them to carry much of the financial risk in exchange for being the sole distributor of this?
7. The 300RR has been out for a while now, are there any companies out there that have already made a body kit based on that? You'd have an easier time getting people together for a group buy for something that's an existing product.
Good luck!