In #16 you can see a small gap between the aluminum ring and the lens, and in #18 you see that the alu ring comes off with the plastic case part. Looks to me like this will provide some much needed protection for the lens. Sure, you'll still be able to scratch it, but it'll be a lot harder.
One thing that I believe is worth mentioning with the replaceable lens cover is that this could open up the possibility awesome camera accessories. I'm envisioning replacement covers with integrated lenses, like fish eye, etc. We could see some cool stuff with this.
It looks lke the cover has electronic contacts underneath it. I'm going to say that a custom replacement would not be an option. Either way, if I don't like it I would purchase a replacement and paint it. I could also just use a product not unlike skinit that would cover it up nicely.