You can want all you like, but unlikely to happen. We have already seen the UE engine and creation techniques do not lend themselves to building long routes - you might get London to Bedford or Leicester to Nottingham but not the whole length. You do realise how long it would take to build such a route, even if it were possible and a commercial team were working on it? AFAIK the only work available which covers the whole route is Thames Trent for MSTS/Open Rails.
Also a less technical reason is Just Trains have very very recently released a large chunk of the route for TS Classic - and DTG are not going to stomp on one of their Partner devs. I think there might even be a community project to infill the Leicester to Bedford gap to merge with the DTG MML
I wonder if Just Trains have expressed some interest in making content for TSW 2. Since Rivet Games made Isle of Wight for TSW and Skyhook games are making content as well, it’ll give them a chance for JT to make content for TSW to the masses, since TSW is mostly played by console users and is way more modern than Train Simulator and that is a dinosaur in game terms. That is if Just Trains have the computer equipment that can handle Unreal Engine.