Ok, ironically, this is the only picture I have of the exhibit at Baltimore. There are seven of these lined up side by side. This one contains I believe 6 azureus. Despite that most recommend to only be kept in pairs, that is really for about 10 gallon tank sizes. This tank is roughly the size you are describing, maybe a bit larger. Azureus and tinctorius will be the most bold and most easily seen by visitors. You can see, however, this may still be difficult as even though they are blue they are well hidden. If you look closely there are one or two at the very bottom of the picture under the plants. I took this at about 8 am at feeding time. Most of the day they stay in the middle to top among the rocks. The tincs in the similar setup are extremely bold as every morning when I go to feed they come to the glass door so there I was having to push them back (literally) in order to keep them from climbing out. Basically, the choice of what to keep in there is up to you. It may be best to keep species separate also if you are not experienced with them.
For the construction aspect, you ARE definitely going to want to have the tank drained from the bottom especially if you are having a misting system installed. This should be easy as you work at an aquarium and I'm sure have plenty of knowledge and easy access to floor drains, etc. The very bottom of these setups were mostly pea gravel for drainage purposes and it is not so messy when soaked with water. A water feature is not necessary although the picture included is one of few that had a waterfall. Most however did have a drip system that dripped water down the walls. This mostly benefits certain mosses and plant growth in those areas.
You will also want to tier the background to allow the frogs to use the entire tank space, and THEY WILL. Also, if you like the rock background, which I personally am a fan of, you could construct one rather cheaply by using a method such as are used in aquariums. Google search: DIY aquarium backgrounds. Here is an example:
DIY Rock Aquarium Background - part 2 | Western Cichlid Forum
Since you work at an aquarium, you may already have some experience with stuff like that. These should be much easier to maintain than having alot of substrate to periodically replace parts of.
I recommend having bromeliads and lots of moss for plants. The aquarium had their own botanist that was able to select plants for the exhibits. To me, that is the hardest part about vivariums. The plants in these exhibits were planted into the substrate which was mostly coconut fiber placed in pockets sculpted in the rock structure. You can also attach them to branches or driftwood that are added to the tank.
Sorry this is so long, but I hoped I helped out with much of your questions. I am sure I have forgotten to address some things so just ask and I will respond.