I wonder, could the HQ building be a much bigger building? Because, then, we could make it as the "locomotive works", like the GWR at Swindon / LSWR at Eastleigh, etc - then it would have a purpose. Maybe it could be a 3x6 building or something suitably large? With a turntable and suchlike.
It could start out some sheds and a lot of fields, and grow over time as expansions are paid for...
If someone is clever with code, perhaps it could confer a 'loyalty bonus' on the company with respect to inhabitants of the town it's located in? Or function as a passenger-or-material-demanding industry in its own right? Could it demand Steel say?
I suppose the trick is to make it not railway-specific... maybe big office building is best after all?
Just thinking creatively... don't mind me!