it seems mostly everyone is on board with the Iron Chef idea. I guess that's the reason why its such a popular show.
It's also universally applicable, anyone from noob to master should be able to yield something cool from this concept. The other two specific ideas that folks are digging are the Themed and Golden ideas. Both of which, imho, are very design heavy, and have the potential to trigger a ton of game-step-upage. IOW, they're difficult challenges, but the results would reflect that.
Also, there are a lot of mentions to exchanging parts, i.e. mailing one or more parts or projects to each other. I/me/josh (just my opinion) think that while it may be fun, it's possibly not the best format to use with a time limit, simply because life gets in the way.
If the progress of the contest is reliant on ALL the contestants buying parts or starting projects, and then waiting for ALL the contestants to ship and receive said parts or projects to other players... next thing you know, it's 6 months later, and JoshSaberFan still has yet to start on his contest entry. And there's also the "screw ur neighbor" aspect. If different people get different parts, then it's no longer an even starting point and inevitably someone will start at a disadvantage, be it obscure parts/project or relative experience in improvisational lightsaber crafting (a.k.a. MacGuy-Fu).
...The simple solution to these problems is to standardize the starting point, i.e. everyone has the same part and no one is at an inherent advantage or disadvantage, and then everyone procures their own - which brings us back to Iron Chef.