[10Minutes]

I think you've put a lot of time, effort, and money into creating this set-up. It looks gorgeous, but many might feel it's not functional. Maybe you don't comfortable about giving up on your effort, but you don't have to feel discouraged - I personally think you can still get a bigger cage than the Ferplast (that meets the required floorspace) and connect it to your beautiful bookshelf. Or, as others have mentioned, keep the bookshelf for a playpen?

The bookshelf itself will still have to be improved on, because I'm just not comfortable with the gap. You say your other pets won't attack it, but what about strays? Rats, etc. from the outside could sneak in. In my house, a stray kitten may occasionally sneak in to the bottom floor, that's why I keep my hamster locked in my room upstairs, where the kitten doesn't even have a chance of going near it. My room may be cramped with my hamster bin in it, but I just don't feel safe leaving her downstairs.

The Ferplast looks like it is perched a little precariously though. You have many other pets, and even if they don't mean harm, it would be quite easy for them to accidentally knock the Ferplast to the floor. I wouldn't even trust myself not to accidentally bump into that and cause it to topple over (because I'm a klutz). I'm sure you're more careful than me, but with so many pets around, you may have to reconsider something more stable for it.

Floorspace-wise, I've read a lot of information that do promote continuous floorspace. Your cage is your hamster's world. The photo depicting the hamster's home network is a very interesting share, but I think the photo shows a home, not a world. You have the space, the finances, and amazing DIY skills, so let's try to give more to your hamster if possible, because it may be small but it's still a life.

I'm afraid you'd probably consider my bin very ugly, but it's fine by me because my main concern is functionality - comfort and safety. My DIY skills are bad, so I don't really care if it looks ugly. BUT you really do have such amazing skills in building that bookshelf and all, I'm sure you have a way to make something really gorgeous. Please try to make something beautiful even better. You have great skills, it shouldn't be a problem to come up with a safe beauty. I really hope you can show us more of your gorgeous work that will be made better with ample floor space and more safety measures.