[geophile]

"Like a startup inside a big company" seems dubious. I have heard it so many times through the years, and it just never pans out. It is basically a euphemism for: you will start with a blank piece of paper and work very hard in a small team. But you will still be subject to big company policies, and of course you don't get anything like startup equity in case your project succeeds in the marketplace. So not literally the best of both worlds.

I'm not saying not to join such a team -- just that you should go into it with a clear picture. It sounds like this could well scratch your techie itch, and seems better than your current position. However, if the chance of a big payoff is important to you, I am dubious.