Let me chime in here....you assume
AGA will agree to loose 6 379s on the stansted route (100% not)
That 378s and 379s are similiar, (in physical appearance perhaps, you'd still need a full conversion..I signed them, they couldnt be more different and TCMS wise)
That TFL/LO would foot the bill to lease extra 315s from TFL and that everybody would be happy to shuffle trains from here there and everywhere to fit Bombardiers mess, and mess with leases, agreements, arrangements for staff, maintenance schedules, mileage plans,...debranding the list is endless..whos paying for all of these logistics? Bombardier? I dont think so. TFL? Dont think so..Dft? Certainly not.
Not you personally but I've read so many posts on this thread about they should/could have picked up 315s/387s/379s, could have trained dispatchers/guards/driver etc etc. The bottom line is this. If it costs, its not happening. It costs. So nothing is going to happen. They will wait. They made a balls up of this 100% but no trains were ever moving anywhere. No staff were going to be trained. The buses are already there. You will see a total line closure before you'll see any of the logistics suggested in this thread.
To draw attention to how anal costs are across TOCs on the NL/GOB/WA, LO have an acquired TFL rail 315, but only because another one was written off, so no bill. It currently runs in multiple as it has defective motors. It wont be repaired until 710s arrive on the WA. Why? Again. Costs. It just about keeps up in the timetable so doesn't cause PPM fines. Theres currently a signal somewhere on the this very network required for a "new train" to run sitting on ballast wrapped up whilst the titans argue over whos pays to install it. Thats reality.
We also must consider that this has been a rolling problem for some time..Bombardier keep trying and keep failing, and gave time frames that kept slipping. As a company what happens if halfway through training your staff, renegotiating your leases etc, orginising moving units spending huge amounts of money, the ORR sign off 710s? Now you really do have a problem.
The reason for shortened 4 car 378's was because Bombardier were happy to foot the bill of the conversion and LO were happy as everything remained the same, drivers, routes, traction etc..then as soon as 710s go live the 5th carriage goes back into your 378 and off it goes down the NLL. Nobodies going to pay for these ideas. Ultimately its the lines users who will suffer, but this is the reality of business, and I can only predict more carnage when they finally do arrive, they (710s) will be dropping like flies with faults in the first year or so, like most other new rolling stock.