I have 12 feet of a 20' steel shipping container for darkroom, so that makes it 8'X12'. That gives me the luxury of having a wet and dry side, with an 8' plywood sink draining into a molded laundry dump sink, and room to the left of that for a 20 X 24 vertical washer. I can say that 8' wide is just enough, actually is good with the 5 X 7 enlarger on the opposite wall. It's an easy pivot to get to the sink. I have open shelves alongside the enlarger, the one nearest it with a tall shelf bay lined with finished flake board to work as a stand up desk for paper and for printing notes. More storage alongside it for photo books and all my misc. supplies inc. camera gear.
I have made small bathrooms work in apartments, in one case with the enlarger literally over the toilet. Had to remove the cantilevered horizontal base from the wall mounted enlarger to use the toilet. Very inconvenient it was.
I suggest considering a means of double decking your sink, so trays can be on 2 levels when you need them, as with large print trays. I modified rigid wire shelving to hinge down in 3 sections over my current 8' sink for this purpose. It turned out to be very convenient and better than a 16' sink would be, with those long walks back and forth. I'd say a double decked 6 foot sink could work just fine. Then you'd have space for print washer on that wall in the remaining 2 feet. It could be over a lowered dump sink off the end of the 6' sink.
Using a lowered standard laundry sink like this is an idea from a long gone magazine called Darkroom. And two levels is sure to give you sufficient tray space even if much of that upper shelving is not used for small prints. An active horizontal wash tray on the sink end of my drop down shelves keeps the lower sink open for trays and works to wash small print runs all by itself.
I visited Ansel Adams' Carmel, California home darkroom with a workshop group the year before his death in 1984 and was amazed at how long his sink was. I'm sure it was over 20 feet. But then he always had at least one assistant, I think sometimes two. I'm used to the double deck system, and I prefer it highly. I added large window screen drying racks over the sink, behind the fold down wire shelves. They fold up against the wall above the sink when not in use.
It's packed in there but it all works very well for me. This is my 5th darkroom over the decades, so i've learned something! i worked for years in makeshift apartment darkrooms, and 2 full up ones in home garages. They all had to be ripped out when moving, taking many months to get working again. I decided that a steel container darkroom was going to be my last. It can be moved intact, if I ever move again which I hope not to do. I'm now in rural mountains where this is possible. Off grid, solar power, satellite Internet, tons of sweat equity.
Best, Todd F.