I really doubt that this is needed, I mean the current fire-truck system works completley fine; and it could be changed & tweaked in a few ways but adding a completley new prop just to 'extent the amount of hose' is completley useless.
The fire engine currently acts as the water source for the hose and can be used in quite a reasonable distance, I don't really see anywhere (other than inside buildings) where getting to the fire engine would be such a struggle. Remember, firefighters also have the unlimited amount of water within the fire extinguisher.
I didn't really fully understand what this idea was, but from what it seems it's fairly useless and not currently needed. Also the template of the idea is not correct; but I'm sure you already knew that.