I personally think its better to have various track types- Third rail, overhead wire, normal and possibly narrow guage. You select track type and get locomotives compatable with that track type. Some locos may be compatable with more than one. Rather than have a hybrid network, just start the whole thing from scratch. But you would have to start with a lot of money to be able to start a track network. In later developement you could have relief of the land and using some kind of system convert that relief into the usage of a tunnel, overpass or bridge, such as over rivers. Maybe with multiworlds coming with Airline Mogul, you could have multiworld games but with difficulty rating, Easy would have Pre-Loaded Track Types, Medium Some preloaded and Hard none at all preloaded. But I think that is a good idea and I think knowing the results with airline mogul this will be good.
