That's a cool idea. Though I see no need to make it VTOL. A simple tug plane, like a glider tug but for passenger aircraft. Really nice thought!
So if you have to keep it, you're trading a bit of efficiency for a lot of complexity.
(outline of a launch: aircraft and tug are connected by cable before launch, both lift-off, gain altitude, cable is detached, aircraft moves on and tug returns to launch site)