Re: Question about passengers
I basically began just as you have. I think you can easily find a good used EB 15 pass van with a V10. I didn't want an EB but that is what I found most of the time. I also wanted a sliding side door and that further limited the available used vans.
It took about a year and then Eddie Persic at Quadvan found what I wanted. It was perfect. RB V10, sliding side door, tow package, rear air and heat, 35K miles. By the time it was converted to 4wd I was in it about $32K. SMB west did the top and solar prewire for another $6k or so.
After some thought we decided a sink was not necessary. We camp outside and sleep inside.
I did opt for a top of the line fridge freezer from National Luna. The dealer is right there in Salt Lake. It sits on a cabinet I built right behind the driver seat. Since the top is at counter height it doubles as a counter if I need it. It works so well for us. It's quiet and draws very little power. The solar panel supplies all the power it needs plus keeps the aux battery at full charge.
We thought about a sofa bed but didn't like the look or feel. The bunk behind the stock bench seat is at window height and is about 4'x6' of 4" high density open cell foam. With the cover it cost abot $600 to have it custom made but it is very comfy. Plenty big enough for us as we are under 6'.......way under! 48 cubic ft. +/- of storage underneath.
I think you will like what you are planning.
Check out "Peckstank" gallery. He has created exactly what you are planning although it's a diesel. He lives nearby and has really done a fine job. I have gotten some good advice from him.
2016 MBZ Sprinter 144" 4wd.
07 BMW 525xi wagon