There's some useful info on housing for Robo's from this Roborovski breeder
The Zoozone sounds like a good option. I guess anything with too much height could be risk for falls so wider and lower is probably better. I guess with a larger zoozone it could be easier to make smaller, if a hamster seems nervy of the space, by having extra enrichment - a third could be sectioned off as a deep digging area for example. So then it would be a smaller unit with a digging area option. I've seen something like that done in detolfs
https://www.flickr.com/photos/125312...6/14203399270/
and you could put a lot more tunnels and platforms in to make it interesting.
Oak Farm Roborovskis
They do say a zoozone 1 style is fine as well, but they also say they can need a lot of space.