The class 707 would be a good idea for this route because it would add more vaierity to this route and be a substitution for the 465 on the Dartford-gravesend services and have AI apperances at dartford.
It would be better included with another Southeastern route rather than being confined to a short 15-20 minute journey on SEHS. Something like London Charing Cross and London Cannon Street to Tonbridge via Sevenoaks and Orpington, where it would be seen operating ~45 minute services with a mix of stopping patterns. Also the upcoming Class 700 would have an almost identical stopping pattern and driving experience on SEHS (with longer services), so adding the Class 707 to only SEHS wouldn't really add much additional gameplay variety.
Also I said it was coming in one of their facebook posts recently and TSW posted a "Spoiler!" gif underneath so yeah, it's an open secret at this point.
so we could COULD see something relating to the 700 pop up in the April 2023 Roadmap which is due on this Tuesday (4th)
this would be a great idea for something like a loco add on bundle 3 pack like i suggested with the 465/2 & 466 as it’s a rework of a train already in game, so it does make sense
If DTG wanted to they could extend southeastern high speed from Dartford to Charing Cross and Cannon Street If it's possible