Have to disagree with you there Barit1, though I suspect your comment is tongue in cheek.
Most of my hours are on RR and P & W, two of the most reliable makers in the business and still there have been plenty of 'return to stand'
Then we have the case of the APU that fails en route to the start-up area, GPUs available there too? Dispatching with a u/s APU will require at least one engine started at the gate if no facilities at the start-up area so the savings are already being reduced as the initial costs may be prohibitive. Airlines shuttling their staff back and forth to the start-up area to suit their requirements? More vehicles on the ground frequency.
Don't see it happening.
M.Mouse I believe the USA system on companies controlling the apron is partly an insurance thing. The airlines lease the terminal space and apron from the airport authority, (think that is the N.Y. Port Authy. in the case of JFK), and the contract requires them to take full liability for all movements in that area, for which they require insurance cover and therefore need to control all movements. Everything from gate to threshold under one GMC would, I think, entail hours of either gate or remote area holding at places like JFK.