Campervan house sounds interesting
Do you have photos? Ferplast sin houses are quite good. They're wood and fit together like a jigsaw and have a lift-off roof. The guinea pig sized one is not a bad size for a hamster (far too small for a guinea pig). It had the rabbit sized one (again too small for a rabbit) for our Syrian and it worked well, but it does take up a fair bit of space in a cage - on the other hand it makes another level. It makes a good nesting box and room for a litter tray inside it.
https://www.portonaquapet.co.uk/shop...hoCsLcQAvD_BwE
It's quite tall so I had it sat on the cage base with a couple of inches of substrate inside it so it was kind of set below the substrate, which makes the door less big.
Here it is in Newt's cage -he stuffed the door up with bedding
Attachment 43297
Attachment 43298