Apologies if this has been suggested before. Is there any merit in updating the GWE route with the Class 345 / Class 802 locomotives and the required catenary on the section of the route that doesn't have it? Two chargeable DLC items and new life breathed into a route. Presumably, there'd be less work involved in this than designing a new route from scratch, though that comment does originate from sheer ignorance! 345's now run between Reading and Paddington as part of TFL Rail's Elizabeth Line, which could be branded as such if licencing allows etc. But yea, that's my suggestion, thanks.
Long story short, GWE will not be modernised for any future electric DLC. GWE is set in early 2016 and DTG have said if they were to make a modern GWE route, it'd be a completely new route. Not modernised over the existing GWE route. Furthermore, as you are probably aware already, GWE is DTG's second TSW route, and is full of both big and small bugs. Which will be very time consuming and inefficient if they were to fix it. It is actually easier and quicker to make a new GWE route than to fix all the bugs in the current version. So to summarise, no, I would not expect any modern electric DLC for this route in the future.
