The west coastway line starts from Brighton goes to Littlehampton and Bognor and Southampton and Portsmouth Harbour through the areas of Hove Aldrington Portslade Fishersgate Southwick shoreham By sea Lancing East worthing Worthing West Worthing Durrington Gorring Littlehampton Ford Barnham Bognor regis Chichester Fishbourne Bosham Nutbourne Southbourne Emsworth Warblington Havant Bedhampton Hilsea Fratton Portsmouth and Southsea and Portsmouth Harbour Cosham Portchester Fareham Swannick Hamble Netley Shotling Woolston Bitterne St Denys Southampton central the route is 62 miles long in leingth the trains that run over the route are the class 158 DMU 313 EMU 377 Electrostar the route has 3 tunnels 1 Hove tunnel 220 yards long Cliftonvile tunnel 220 yards long Southampton tunnel
I'm here to Bump this and add that Havant to Brighton would be a sensible route length. Class 377 and 313 will date it to the early 2010s. Both of these trains are already in the game. The journey takes around an hour on a stopping service and is very scenic.
I think there is more of a chance that DTG would make the East Coastway line. Having done some of the groundwork in the TSW Brighton-Eastbourne route it could be a possibility. Some might argue that it would be a conflict of interest having the route on both TSxx & TSW platforms but who knows, if DTG saw a profit in it....