I have always used a fixed hose reel and while there has been times I have thought it would be easier with one I could lift out, most of the time I manage fine.
Another window cleaner I know used 2 reels, one facing out the back of the van, the other facing out of the side door in front of his tank. That certainly has its advantages, but I guess you would need a bigger van to be able to do that.
Over the years I have occasionally mulled over the possibility of using a pickup (with hard top) for work and had thought that mounting the hose reel on the inside of the drop down tailgate, mounted on some kind of swivel would be a good idea. Maybe someone out there uses a similar system?.