[throwawayboise]

You still need enough reserve power at the end of a flight to do a rejected landing/go around, or you won't get certified. If you are relying on some kind of catapult, rail gun, or rocket assist to take off, not sure how that happens.

[sokoloff]

An early rejected landing still requires less power than a static takeoff, so you could get by with a mix of craft and assistive power.