The London Underground is already a thing in the game and it would be cool for the second most popular underground service to be a route in the game.
The glasgow subway is considered popular? Also the GS is just train version of: You spin me right round.
Don't think I have ever heard anyone call the Glasgow Metro "the second most popular"? At least the Bakerloo has the mixture of above and below ground, the GM is entirely underground and mostly computer controlled, so it wouldn't be very interesting at all.
Yeah, I live near Glasgow and have been on the subway so you'd think I'd be all for it but it's very boring. You'd be better off with the North Clyde and Argyll Lines bundled together. Mix of underground and overground in Glasgow and it's got ScotRail trains which, personally, look nicer.
Set it back in the 1960's or early 70's pre-modernisation with the old stock and no automation, scary narrow island platforms and it would be worth a budget price purchase.
Whilst i am not against ATO routes, i personally think setting the Glasgow Subway Pre 1977, with the original 1896 trains,as a Cable hauled route would be quite intresting to see
By what metric? I can think of a few others that are better known. NY, Paris, Tokyo, Berlin Glasgow has the problem of ATO and it's just a short circular.
Even better would be to have it set when it was a cable system. That would be fun for a stocking filler route.