I have a bluebell as a shelter for one of my rabbits, but I have permamently blocked access (so it’s effectively two separate hutches now) by screwing a piece of wood over.
To make a ramp hatch, you can screw a piece of batten across the back wall for support, then using another piece of wood slightly larger than the opening as a hatch and screw hinges on. Pop a hook or bolt so the hatch can be clipped open during the day.
In my piggy hutch came with a hinged ramp hatch. In order to protect the wood when the hatch is closed , i lay a piece of plastic over, cover with newspaper and then hay (and then remove it in the morning to be able to open the hatch again)