-Good start but there are a few problems, the first one I saw was the before mentioned aspect of having to take apart the whole thing to change mechanical media.
-The second and an even more important aspect of the filtration process is that you're bio media should come after your mechanical filtration. You don't want to have your bio scrubbers accumulating all those nasty particles.
-First thing I would do is make the first chamber the mechanical area and have the eggcrate just as shown. Also, you're going to want almost all of your bio area filled with water.