When I built my darkroom I had the sink designed to be somewhat deeper so as to prevent any splashes. Also it has three removable tops that can cover it and be at the same height as the counter ("L" shaped as your plans) to give extra counter surface when not in use as a sink. An exhaust fan system and canister water filter (if your water quality isn't the best such as well water). Plenty of well placed electrical outlets. Storage under the sink for chemicals, trays and stuff. Blackout system for the glass door. I placed "L" hooks above the door and attached blackout material to two dowel sticks one for the top and one for the bottom as a weight. I can roll it up and remove it when not needed.