I prefer alternate histories that are plausible rather than alternate world. The example I would use being the connection between the two halves of the Piedmont & Northern. I've toyed with creating a section of what might have been if this connection were approved. Would it have been electrified or, given the late date, would it have skipped right to dieselization? Those are the interesting questions becasue they almost happened.
Here's something that was seriously considered in real life: A merger of the Akron Canton & Youngstown with the Detroit Toledo & Ironton. In actual practice, the two roads had a very busy interchange at Columbus Grove, Ohio where tires and wheel rims were brought west from Akron on the AC&Y and turned over to DT&I for forwarding to Michigan auto plants.
It would be interesting to imagine how the two roads' rosters might have been combined. AC&Y's mainline steam power was light Mikes; DT&I's used much heavier Mikes and Berks. AC&Y dieselized with F-M hood units on the mainline and Alcos in the yard; DT&I dieselized with EMD Geeps on the mainline and SW's in the yard.
Would the paint scheme have displayed a combination of AC&Y yellow with DT&I orange?
Tom