The idea will work.
How deep is the skimmer supposed to be? ie...5" or 6" ect...If the skimmer is going to go in that first chamber then the depth is very important. It is a good chamber to put the skimmer in as the water level wont vary.
The second set of baffels you have with the gap tward the bottom will work. Don't go any less then 1" gap IMO. It could pose a problem with stiring up the sand bed as all the flow will by directed across the top of it. You could eliminate them all together and gain more room for the return pump chamber. The return pump chamber is where all the evap is going to show up. So the smaller it is the more frequient the water addition will have to be to keep it from running dry.
What material do you plan to use for the baffels? If it is a glass tank I recomend glass baffels.
The Rio you referenced to. I hope the "hf" isn't the estamated head height for your tank. How far will the refug be below the tank?
What size plumbing do you intend to run?
How many outlets will the return have?
How are you going to drain the water from the disply to the refug?
More to come after you answer those.