DTG could make blank services where we can choose what stock and livery to use and it would fill in layers to the timetable
How would you imagine that though? And how would the AI handle those services? I mean, I'm personally all for something like that, although slightly different. My own idea would be to have the standard timetables that can not be deleted or edited by anyone other than by the dev's, and you can copy those to make your own layer and edit it any way you like, at your own risk of course. Basically a lot more advanced version of scenario editor.
I was thinking like pre-made services which you can choose locos and your on liveries for and layer on to the timetable of routes, for example layers that follow the same route as the Heathrow express trains from Paddington