If you live near a hardware store like home depot or something (depending which country your’e from), they can usually cut wood to size for you if you were interested in making it yourself. That includes sheets of plywood and lengths of pine.
I have two main concerns with the condo, the first is the ramps. While carpeted ramps are good because they provide more traction, ramps take up a lot of space and the space at the end of them is a little squashed if your rabbit has issues going down them easily. The second is the carpet, perhaps your rabbit is already fine with carpet, but I know for a fact that some rabbits absolutely love to chew on and eat carpet which is very bad for them. Can you be sure that your rabbit won’t do this, and will you be able to remove the shelves and replace the flooring on the levels if he does? Otherwise, the only other issue is the space to stand upright as you have already mentioned which you said you would be able to remedy.
You would still need to put a sheet of coroplast or something on the back of the cage to stop hay and poop falling off the shelves etc, but with the cage on wheels it’s not a difficult task to pull it out and just sweep or vacuum behind.
At the end of the day, this cage still comes flat-packed so you would still need to assemble all the grid squares and attach the shelving units etc. Otherwise, it still looks like a well made product in terms of what they’re offering. I just prefer to set up things like that myself so it’s completely custom built to how I want it which is what I did with my 5x2x3 condo. At the end of the day it’s really about what works for you and your rabbit. How much hopping space does this cage offer in comparison to his current set up? I’m assuming he’ll still have access to the play area when you’re home and the cage is just for night time and when you’re out.
If you’re not sure about building one yourself, go through the steps of what you would need and how you would want the cage built, what you want to use for flooring and flooring surfaces, and work out what you can and can’t feasibly do at your own place. Technically the bottom level doesn’t even need a solid floor, you can just use carpet, fleece blanket or linoleum flooring extended beyond the base of the cage for the surface on top of your flooring in the room.
Also, in regard to those bunny abode condos, I would probably avoid them because the door openings are quite small and it would be a pain to clean out and access. Also much less customisation, whereas the ebay condo, if at a later date you decided that you wanted to add onto it or expand it, it’s very easy to do so by just adding more grids and taking away some existing ones.