As this was one of the most popular routes on TS it should have a chance on TSW as it boasts new rolling stock and a new facility at three bridges!
How about B.M.L. between Brighton to Victoria or London Bridge; with Class 377, and 700 railcar? And yes, BML is the best route ever. https://en.wikipedia.org/wiki/Brighton_main_line
London to Brighton would be nice, as long as all 50 miles of it is made. Its one of the routes in TS20XX that has aged pretty well. Even in 2018 (heading into 2019) its a route that is still really popular and used quite a lot. If DTG made this for TSW, I would like to see the route from East Croydon to London Bridge included as well. That would provide another big terminus station in London to go to and would have a lot more services to drive.