i know what your saying ian, i hate that especially when your winding in you have to grab the dirty hose and i usually use a cloth to clean it as i real it in but its annoying when you turn up at the next job and its all tangled up and stuck in the sides.
I will probably make mine with this, but as a seperate part, you could weld it onto the reel, like the off the shelf ones have, but im going to have one a bit shorter than the width of the reel centered so it can wind on completely and mounted flush with the floor.
You could cheaply use a decent electric drill, take a couple batteries along for it, and the right fitting in the end so you can simply push it on and off to reel in. Im going to have the motor mounted near the bottom with a chain drive.