Creating TechStars sounds like a great way for VCs to get the pulse on what the young entrepreneurs are thinking about. Even if they don't select anybody, they will have a lot of information on probably 10 to 20% of people who cross-applied to both YC and TS. But, the good part is there is more incentive on YC to select the best people, regardless of idea, including "no idea", before TS does.
I think not selecting anyone would be bad for reputation. They're already starting out "in the hole", so to speak, and failing to select the ten they say they're looking for would confirm evilness for some people, and raise the question for others.