That’s the west Coastway , so I think it would be better to make the WCW then link it to the BML and ecw
No it isn't, it the Arun Valley Line + Three Bridges - Gatwick and Ardunel - Bognor Regis (probably would include Littlehampton as well). It's a different route
Depends which way you go from Gatwick from , continuing down the BML towards hove , or down the Arun valley
Chiltern Mainline London Marylebone to Birmingham, but I fear it would be too long and DTG don't do long routes in TSW 2.
If it went past Hove it would just be Brighton - Bognor Regis (a strange end point in that case). No point duplicating a large part of the BML.
I know that, bit it's a strange place to cut the WCW off. It makes more sense to go to Portsmouth, no? Or even better, Southampton with GWR involved.