Unsure if this is what this forum subsection is for but I have 2 route suggestions. I'd like to see London Victoria to Portsmouth Harbour route with branches on both ends with extension to Brighton on the London end and extension to Southampton Central on the Portsmouth end. I'd also like to see the entire London Underground in TSW.
I have suggestions of routes here from Brazil, more specifically from São Paulo CPTM trains, all lines and São Paulo Subway.