wet

And bacteria (and I would argue that in a high uptake moderately stocked tank there is little nitrifying bacteria / not enough to care about vs. plant uptake to begin with) will live where ever it can. While porus pot scrubbers are great, I'm not so sure its better than whatever is in your canister or, say, natural driftwood. Its not as if more media means you will have more nitrifying bacteria: there is as much as can consume available NH3/4/NO2, and if you have an excess of media in any one section of your filtration I'd bet a nickel they would just keep colonizing at that one section.

What your plan will gain is increased oxygenation, which depending on your goals can be very good, and to maximize this you will want to distribute flow across the surface area of the wet/dry section as evenly as possible. Elsewise I think you gain nothing. A bigger chamber for a sump/more water volume though...

As a tangent, I have thought about a low uptage tank with very high surface turbulation with the goal of constantly equalizing CO2 (or however much we can grab) with the atmosphere. Now, under high light and vs say BBA this would be bad, but under lower light and lower uptake its conceivable such a design would guarantee CO2 is never a limiting factor (nor O2 for animals, of course).