The problem with 769's is the use of the old traction motors (DC▸ ) and old (modified) traction control package where as the new Hitachi trains in Italy will make use of modern polyphase (AC) traction motors with variable frequency drive.
The Hitachi units I suspect are on offer to the UK▸ market, however we in the UK (or at least the DfT» ) seem content in trying to make old stuff do something it was not designed to do. Other manufactures like Siemens etc will have similar offerings to Hitachi
That will always be the problem until something radical, like changing all 750V DC for 25KV AC, happens. The 769 is in essence, IIUC, a 30-year-old bi-mode based on 80-year-old technology with a diesel engine and alternator to provide power when there is neither third rail nor OHLE. It's a new patch on an old coat, designed to run as efficiently as the least efficient part will allow. I'm surprised there isn't also a battery carriage and a hydrogen tank to make it truly future proof, and earn a broadgage indulgence. It's better than no train, but come on - this is the 21st century, where diesel is a Bad Thing. Put some wires up.
IIRC▸ , the story with the 769s was that in theory they hit a 'sweet spot' of being reasonably modern, crashworthy etc, but not so modern to be software-driven, they had couple of carriages with space underneath and a 750v bus running along them, so if you added a diesel genset that could mimic a third-rail power supply then lo and behold you could have a 25kv/diesel hybrid at bargain price and very quickly.
It was probably always going to be a gamble, but they had to get the new kit to fit, work and not interfere with signalling etc. It also seems that no-one talked with the guys who produced the original electrical gubbins, who might have told them of a few pitfalls and that getting two gensets to work in parallel is actually quite tricky. It was perhaps even more optimistic to be thinking that some clever switchgear could leave the shoegear intact turning them into tri-modes.
The problem with these projects is that at what point do you say "sod it", pay off Porterbrook and start chatting to Stadler about what they might be able to deliver in a couple of years after the more pessimistic have received their orders.