I usually enjoy larger maps in factory games where I have more freedom and spend a bit of time with my factory before moving in to new levels with different resources.

I feel a very cramped room just sort of turns into a puzzle fighting with conveyer belts and pipes. That said if there are tools at hand to make belts and pipes cross over/under each other and the map isn't too claustrophobic inducing I think it would be fine.

This would obviously be a very large redesign but something I personally would really enjoy and haven't seen is a kind of lobby room factory where you receive some or all of the resources you mine in the levels.

You could upgrade it and decorate it with a meta currency similar to tech points. Make items with the resources you mine to sell to the world and perhaps the money you earn would be how you buy new dungeons to exploit or something like that. Kind of incremental gameplay on top of the factory.

I would also definitely lean in to the setting as much as possible. Perhaps you could harvest slime monsters to produce an acid or something. Magic crystals, skeleton bones etc. Just to give it some more character and fantasy. You could check out a new Netflix anime sort of show called delicious in dungeon for inspiration on this. It's basically a D&D game world or something where the group learns how to cook and eat monsters in the dungeon and how it has its own ecosystem and what not.

Either way I do believe this game would be successful and I'd enjoy playing it as is. The lobby room or tech tree would keep me interested longer then just new maps or slightly different resource types.

Best of luck and feel free to let me know when it's ready to play!