Finding the ideal cage is so tricky! For the hamster, for the cage site and so on. Access is also an important issue, especially with a shy hamster maybe. Some people use cage doors on a bin cage instead of mesh - although that means finding an old cage door and might be tricky securing and have it as an opening door.
If you think ventilation could be limited via shelving, then cages do have the best ventilation really. Something with a big front opening with small bar spacing like the Savic Mickey 2XL could be ideal - it's a shame it is so expensive.
The Rivierra Varrazze mouse cage is slightly smaller, has narrow bar spacing and a smaller front opening door. It's 40cm high though so would need levels. The base isn't as deep as the Mickey 2XL though, for substrate. One of the reasons I like the Mickey 2XL is it's not too high and has a good deep base (about 16cm but you can pile the substrate higher in places as it doesn't fall out of the small bar spacing.
There's also the Skyline Leon which has 6mm bar spacing and two full levels.
Deep substrate, good front ventilation and front access are tricky in some ways - but not impossible!
Most cages have a maximum base depth of 16 to 17cm and a lot of cages have much shallower bases. I think the Duna bases are no deeper than this either.
The Duna Fun Large may work for you if you need the side ventilation and a reasonably deep base, although still top access, but I'd also recommend blocking off the tubes and using your own items in the cage rather than the supplied shelves and ladders, if it was me. So it can be set up for good cover for a shy hamster, but also easy access for you to get to items in the cage, or the hamster.
Ooh I almost forgot! A couple of great cages that are smaller than the Savic Mickey 2XL with narrow bar spacing and deep bases! I was looking at them when looking for a smaller holiday cage for our Syrian. Both have not good access - eg small doors on top - but the bar tops are not high and they are really easy just to lift the whole top off, which is what I did. Because the cages aren't tall the top doors are good for changing food and water quite easily or moving the odd thing.
So - the Ferplast Kios - it's a mouse cage with 7mm bar spacing, a good deep base, only 29cm high. Not too expensive
https://www.amazon.co.uk/Ferplast-Ki...s=FerplastKios
And this one - it's the one I got for Charlie's holiday cage. Not the wire wheel obviously, but the built in house is great and gives lots of cover. It would need a shelf adding as well to give more cover. Bar spacing also 7mm and a good base depth.
I put a corner shelf in at the front (other end to the house) and another longer shelf along the back, so there was quite good cover over the cage. Internal height is about 32cm. Also not too expensive.
https://www.amazon.co.uk/Skyline-Ted...ds=Skyline+Ted
Both would give low height, not as big as the Mickey 2XL (if that's an issue), top access - but limited top access - may need to take barred top off occasionally.
This is how I had it set up as a holiday cage for our Syrian - bear in mind it has a big wheel in which you wouldn't need. Neither of those shelves is very big and you can get a 40cm x 40cm corner plastic shelf for about £6.
There's also the Skyline Leon. I think it is quite small but it does have full levels in and front opening doors. Base isn't as deep as the others.
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