Also frighteningly ambitious is the prospect of any meaningful startup driven disruption in the energy industry. Which is a worry considering how desperately disruption is needed.
Electric aviation and space launch. See our web-site, http://electrictakeoff.com, for details. We are looking for collaborators, co-founders, volunteers, etc.
I agree with PG that ambitious startups are better. However, I think engineers should focus on sectors where the customers are dissatisfied. Aviation seems like a good candidate. Most people dislike oil dependence also.
Tactically, we are aiming to fly advertising banners as a short-term path to revenue. The next market would be air freight with prices lower than diesel trucking. Passengers would come last after the technology is proven.