The thing that makes me most concerned when I look at builds like this is how wet the conditions have to be to keep that moss going. If, somehow, you could do the same thing you are doing but with no water at the bottom, maybe that would be acceptable from a frog husbandry perspective. You would have a lot harder time maintaining correct humidity levels without the crutch of having standing water in a reservoir under the substrate as most of us do in our builds, but it might be possible. This assumes that the ventilation is more frog-appropriate rather than moss-appropriate and that the moss would be ok without the standing water. My experience has usually been that either the frogs or the moss do well in my tanks. Occasionally, it's both, but not very often. So, maybe a soil-less build could work without the standing water in the bottom? It would be less likely to wick moisture to the point that the frogs have trouble finding dry space to stand.