Looks like you are also using c&c cage (by looking at your picture - we use it too) try making your own box (or asking someone else if you don’t have all the tools)
you can also acquire free materials if you post on your Facebooks local SwipSwap group!
alternatively we use another place entirely for pregnant does - they have ground hutches not raised ones
We have our doors on our raised ones open 12x24 not much extra room but some
i also have inlaid liter pans on our raised hutch that my husband and I worked together to make sturdy (with L brackets-fit into c&c connecters) but removable!! To clean or if needed .. the placement is closest to the door so its actually got a 12x12 opening underneath the 12x24 door (unfortunately my Queen rabbit Reese quickly figured that as a easy way to get out of her hutch she’s the smartest of the Bun-ch)
My intention was to fill it with hay and surround it with hay so maybe they would dig down (this was before all my many expansions) - Nope no one - butttt I have inside/outside liter trained rabbits! - Sooo if you don’t you could see if this works (and let me know please haha)
we have all different size nest boxes and hutches - were in south Florida - my biggest problem is flooding and snakes thankfully noooo snakes have ever eaten any kits to my knowledge but I have caught a few black racers (cut their heads off every time so it’s not the same one)
Our pregnant does have 2’x4’ ground hutches - not raised hutches - we think it’s more natural and safe feeling for them (just a superstition) - we don’t use them in flood months or when expecting heavy rain they can come inside free roam or 2x4 c&c and use nest boxes
Not sure how much - but I hope this helps - either way let us know what you decide to use!