Yeah, I figured that would probably come up at some point. I don't have any specific plans to add joystick support, but it's something I'm open to. Unfortunately, I think it's going to be a not-insignificant amount of work to make the game usable with a joystick instead of a mouse. Right now the UI doesn't support keyboard navigation at all, and I'm unsure how well the game itself would play with a joystick. Plus I don't have one so I don't currently have a way to test anything.
I'll keep it in mind though and see if I can make it happen at some point.