I think this is a very attractive idea. Developers seem to be buying Macbook's in droves yet a well equipped Linux desktop is just as powerful and in many regards moreso. Most users simply don't know about the number of fantastic dev tools on the Linux desktop. A marketing effort showing the fantastic tools would go a long way to swoon the Macbook crowd. Not to mention the fact nearly all these tools are 100% free *and* open source.
Creating a single image to rule them all is obviously a difficult task. You seem to be making good decisions. I personally am a Fedora user so this initiative doesn't directly align with my preference right off the bat, but I understand your choice. I hold hope that this effort indirectly results in better upstream driver support for the Dell XPS 13 that Fedora and other distros can enjoy. I would be happy to vote with my dollar if that were the case.
For future hardware considerations, more RAM the better. I am a Java developer so it seems one can never have enough. Also as others have said +1 to much higher resolution displays, 1680x1050 is the minimum to be practical.