So they're using double doors for rear access? I wonder if flip down ramp would be better, especially when trying to carry casualties on stretchers into the vehicle.
That'd be a solution looking for a problem.
Loading stretchers is actually best done at waist-shoulder height, while full standing. Handling a stretcher load lower than waist level and/or bent over is back breaking
Adding a ramp doesn't really make it better here. Vehicle ramps are actually slippery things. Not the best underfoot conditions when trying to load a stretcher. I've seen sim casualty dropped off shoulder height trying to load onto a 8x8 ambo (with ramp), no fun. It also doesn't help that in ramped ambulances, the stretcher has to be brought into the vehicle and then side-on lifted into the rack rather than end-on from behind the vehicle - which means the bearers have to do some heavy lifting inside the cabin while bent over.
Rather than adding a ramp to a vehicle that doesn't have one built-in, better to spend the money on putting in a self-loading stretcher rack - like so ...