While I applaud the effort, this seems like a very short-sighted project. Design is not about how things look, it's about how things work to advance a set of goals. And it's very difficult to know how things work without research and exploration. Any new design would start with reviewing stats, business goals and the competition. Projects that don't do that should more-aptly be called "re-colouring" or "moving things around to be pretty."
Incidentally, there was a designer who did a "redesign" of the American Airlines site a while back and ignited a fire store. The response from one of AA's designers is worth a read: http://www.dustincurtis.com/dear_dustin_curtis.html
I dont think "re-colouring" or "moving things around to be pretty." really applies to this series. The redesigns seem really effective and are based on a specific criticism of the site (“doesn’t make you feel confident in their claims of what their app does.”).
In web design that's often frowned upon because this isn't the "end" of the design. It has a whole interaction component that isn't being addressed by a picture.
The letter from the AA designer doesn't support your position at all. The reason he couldn't do a major redesign of the site was because of all the bureaucracy making it impossible. That shouldn't apply to a YC startup.
Incidentally, there was a designer who did a "redesign" of the American Airlines site a while back and ignited a fire store. The response from one of AA's designers is worth a read: http://www.dustincurtis.com/dear_dustin_curtis.html