I am suggesting Journeys that consist of a series of scenarios built for different routes. for example a Freight journey made from a Goblin line scenario driving a freight train from Dagenham Dock to Gospel Oak, a Mildmay scenario from Gospel Oak to Wilsden Junction and a WCML scenario from Wilsden junction. Where the routes are set in different time periods only locos and trains from one time period would be used for all scenarios. For example a Pendolino driving from Euston to Carlisle with only Modern AI. Where routes are not contiguous the start time of the next scenario would take into account the time it would take to drive the distance between routes. Although this would not be a seamless joining of routes, and there will still be loading screens, it does take away the need to go to the menu and you stay in a set-up cab. Also I think a scenario scale timetable makes it feasible to use non-native traffic on a route e.g. 80's Euston or modern Carlisle. You could start a Journey in Glasgow and finish in Euston.
yes please for scenarios. Services, no. Those routes have their own services/time tables and trying to merge them together. I heard/read is a headache.