>>1484598>>1484605I'd probably go British, a 1980s time period would be good because they had a good variety of interesting locos, both electric and diesel, and an active steel industry that'd fit your "heavy industry" requirement well. It was also an era where pretty much everything was run down and grungy and I think that makes for much more fun in terms of modeling. The OO gauge scene is really active and well developed and if you're American it's much easier to get into since everything about it is in English. There's a good youtube community for British OO gauge railways too, check out DaveClass47 and Everard Junction for really nice examples of stuff that's about the right era.
I really want to do something similar myself, I just don't have the space or the budget right now.