I think the Plaza would be better for a Syrian than the Maxi Duna and the Bucatstate isn't big enough. I am not sure if there is a larger version is there?
I understand the concern that he may continue bar biting if he's in a barred cage and not wanting to waste money. Another member on here recently had the same issue and her hamster stopped bar biting once she was in the Plaza cage. It continued (the bar biting) for the first couple of days - maybe habit or the stress of a cage move, but then it stopped. They have more to do.
The Maxi duna is nice but the height is limited for a Syrian wheel. It is still a nice cage but harder to add as much enrichment perhaps. The Maxi Duna is also quite expensive these days. The Zoozone large is virtually identical but has larger bar spacing so the lid needs meshing and the lid can be a bit clunky but it is cheaper.
You're right though there really aren't any tank styles to choose from without diy. Some people use detolfs which only need a lid making. There is the Living world eco habitat but that costs over £200!
One option with the plaza though is you can get perspex panels made to fit it (Viking Laser) - these are intended for deeper bedding (so it doesn't spill out of the cage) but they can also prevent bar biting. Unless of course the hamster decides to climb on a shelf and bar bite further up.
But Viking also make full perspex panels which can actually turn the Plaza into a tank! It is not cheap - it would be like the cost of another Plaza, but it is an option if the hamster does continue to bar bite. The theory is that they stop doing it when they have more space - providing there aren't other stresses like cleaning out too much or not enough enrichment, or wheel too small etc.
It would make a lovely big tank style if you did end up needing perspex panels and a much better cage than the Maxi Duna due to more space and options for split levels etc. But then anyone buying the cage AND the panels it could still end up as expensive as an Eco habitat. But - it would still have a large front door which is a big bonus on a cage (IMO).
Transform your Savic Plaza 100 with crystal clear acrylic complete cage screens. Replace the bars on your Plaza with almost invisible screens.
www.vikinglaser.co.uk