Russians are likely the people who have the most experience with that so far, and they opted for other solutions despite throwing spaceflight-money at the problem:
https://www.buran-energia.com/documentation/documentation-ak...
Maybe with modern technology and computer-controlled flight it could be made safe, but getting into that would completely defeat the point, which is to find a cheap way to move the plane.
If would be in the need of a good Valhalla track, I would volunteer for the airstart of a civilian pax hauler brought airbourne by a pack of Mi-26s
Glide restarts of engines are possible (if not core locked) but it also isn't something done very often.
IMO the bigger problem would be needing multiple helicopters pulling together - wind or the jet's engines might pull the helicopters enough that they'd crash into each other, & you'd definitely want to start the engines before freefall..