Re: TPF and Kepler are both great ideas
Kepler should incorporate this technology, after all the very means it uses to confirm a planet (passes in front of the star) would give it the inherent ability to analyze the planet's atmosphere for nitrogen, oxygen, argon, etc.
Time is money. If we have to spend another 4 years staring at the same piece of sky just so we can catch *the same planets* passing in front of their star, that would seem to be a waste of time. We would be doubling the mission duration, doubling the cost, doubling the launches, doubling the chance that the followup mission would be delayed.
Forget TPF - Atmospheric analysis should be done by Kepler.