I think a fantastic route to add to Train Sim World 2 would be one of the Merseyrail lines. This being either the Wirral Line or the Northern Line. The network has a variety of underground and outdoor routes and has plenty of opportunities for route add ons. The Wirral line runs between Liverpool Central to Chester and West Kirby and back via the Liverpool loop. With branch lines to Ellesmere Port and New Brighton. The Northern line runs between Hunts Cross and Southport with branch lines to Ormskirk and Kirkby. The trains on Merseyrail network are currently class 507/508 (which are very similar to the class 313 add on) so I think this route should hopefully be possible. The network also has class 777s coming soon which would make the route for TSW2 even more exciting! I should really hope this route becomes available to TSW2 soon. It holds plenty to potential for a variety of trains, add-ons, underground and outdoor routes. And overall would be a great route. Please let this happen dovetail!
We would either get the Wirral line or the Northern line, both in the same route is too big a project like said above. I would favour the Wirral line as it would be quite interesting operationally; trains would form services from the branches to central Liverpool, traverse the loop and head back out to the branches again, allowing you to make a full return journey without switching cabs.
You are making 120 km out 75 mi here surpassing Riesa-Dresden with the Flughafen Dresden Klotzsche Branch completed by 15 km 9mi which is 105 km 65 mi.