My concerns would be…
1) what’s holding it down? There’s no steel chassis. The plastic of the tank has (virtually) no structural strength, so in a crash it would almost certainly break loose.
For this flat tank, the danger is reduced as it is low down, but in a crash it could still do some damage and pose a danger. (The other, taller tanks are death traps in my opinion. I would NEVER drive one of those around myself, let alone give one to an employee, whose safety I’m responsible for)
2) the hose reel is subjected to quite powerful forces, especially when reeling in at full speed and the hose gets snagged on something. I use a webbing strap which is wrapped around the steel frame of my system (which I’m turn is bolted to the vehicle’s chassis) to stop mine moving about. The plastic of the tank isn’t strong enough in my opinion. It’ll probably bend it over time, then tear it.
3) strange position for the controller! It would be better tucked out of the way somewhere. You don’t need to access it very often, the pump speed is a ‘Set and forget’ thing, and the filling control isn’t needed at all while working. It’s very vulnerable there.
4) there are no bars on the reel to prevent the hose from falling off the reel to one of the sides. I would bet that would happen so often it would be infuriating.
5) I don’t see the benefit of a flat design like this. Why would you want to take up all of the floor space? It will end up having lots of space above it, but why would you need that?
Personally I would find it more useful to have extra floor space in the van than extra ‘airspace’. Maybe I’m missing something?
What this tank may be useful for is a truck bed?
Just my thoughts.