I found that I really don't need that much to work well. The only thing I regret to date is that I haven't installed a proper electrical circuit dedicated to the darkroom.
I need a really sturdy enlarger stand, so I built that. Good safe-lighting. Light proofing. A sink. Room for all trays. And lots of storage space.
I think the rest is 'nice to have'. I really ought to post a portrait of my darkroom into the thread mentioned above. It's basically just a section of an open plan basement with the windows covered up, and a hinge on the door to keep the cats out.
Good luck with your project!