I may be a mere engineer, but I have been onboard two TriStar two engine ferries.
We did all the prep, boroscopes, new nosewheels, ATM duct clean, dump toilets and water, remove catering and cabin crew etc. Then off we went. With the RB211-22B we could manage MCT-BAH but not much further, with a RB211-524 we did KHI-BAH.
What i remember most was that there was no V1. We had Vr and V2. I asked the crew why and the answer was that if the second engine failed before V2, we were going in the sea. Why do you think you boroscoped the good engines? The steps were already off so I stayed on board.
If GF (and Lockheed) were prepared to ferry an aircraft like this, why not a one engine ferry? Can't be a lot worse.
The drill was wing engine to 100pc for one minute then back to idle. Then Centre engine to 100pc for one minute, then let off the brakes. Advance the good wing engine N1 in line with speed, i.e. 60pc N1 at 60kts. Any more and you were off the side of the runway (It happened once in JED in 1977).
In my 11 years at GF we never changed an engine away from a main base.