I've always felt the same way about moss. Some people will refuse to acknowledge the risks of it and say Germans use it so it must be fine, but that completely ignores the questionable at best edible aspect and the very real issue that it poses to hamster respiratory systems. There's also a potential very harmful negative environmental impact from the use of particular mosses, which is also a very good consideration to account for.
A very small section with a thin layer of 100% coconut fiber could be an acceptable choice if used appropriately, but it also holds moisture which is why you need to be careful of just how much you use. However, this option is known to be safe if ingested and unlike moss is a highly sustainable renewable resource(many companies manufacture coco coir/coco fiber/etc with what is essentially wasted coconut husk from the coconut farming industry - things like coconut milk and oil for example).
In the USA, a good coco fiber option is this:
https://www.chewy.com/zoo-med-eco-ea...onut/dp/123767
Keep in mind with wood you'll want real solid wood of a known safe species that is kiln dried. I wouldn't use any kind of plywood since there are potential dangers if chewed and ingested.
A good alternative platform are these:
https://www.petmountain.com/product/...?variant=16651
I'm not typically a fan of Kaytee, but they did very well with that particular product. Be sure to pick the right size for the individual hamsters though, I would stick with medium for a robo and large for a Syrian. This would work great for chewing prone hamsters since they can't be chewed and destroyed, plus in my experience they've been relatively easy to clean.