The one I've had in my head for a while is a "Factory" simulator. Like, think Factorio or Satisfactory, but grounded in reality, instead of on an alien planet. You own a factory and take contracts to produce stuff, and have employees that run everything. Occasionally, you'd actually need to tear down and re-tool chunks of your factory to accommodate new production. Initially, you contract-out raw materials, but maybe, eventually, you source and process them yourself.
I’m a kitchen designer and use an app called 2020 design to do cabinet layouts.
Thing is, we’ve got 3D models of every single cabinet we sell, plus a lot of name brand appliances.
It would be fun, for this factory game, to use real machinery from real companies. It would be a pretty massive undertaking to simulate all those machines, but existing CAD models could be a start.
I imagine there'd be IP stuff to worry about. Like, you and me probably think it's just a box with a door on it, but the company that designed it sure won't...
But I've thought myself that if you mashed up CAD files for various widgets with a UI made by a good game designer, you could have some extraordinarily useful business apps that are a hundred percent better than what's usually on the market. I can think of multiple games with base-building in them that are easier to use than business apps that honestly do very similar things.
I have to imagine there's probably some market forces at work that prevent this from happening.
Semi-related, but I read somewhere that there's some military equipment out there that uses a video game controller b/c that was easiest to train young recruits on since most already were quite familiar with it.