Dave,I'm thinking about something I can drill a few holes and bolt the hose reel on.Welding or fabrication shouldn't be necessary.
Mike,you can bolt the hose reel on one side to allow one of the rear doors open.Or use the side loading door if there is one.It's going to carry the hose reel,hazard sign and the pole outside the van so you shouldn't need access to inside.A bucket holder might be possible,if you trad some windows as well.
Have a look at this video,
http://youtu.be/DaBFgXlgAs4Bak rak is the cheap copy of that i think.
Another idea is to keep it simple and use something like this (imagine a hose reel instead of that winch
)
http://youtu.be/yRWHhejWMdghttp://youtu.be/gun-MHJPfnEhttp://youtu.be/qOlP3Im7bvI <-- He is jumping on that rack