In general it looks like a workable design. I would recommend these modifications. Instead of using all that space to house a small pump, use a piece of PVC pipe, old margarine tub, etc. Here is an example:
http://www.dendroboard.com/phpBB2/viewt ... 6821#46821
Second it may be more challenging to adhere things to the egg-crate on your divider because of its open grid like structure. But, if you go with PVC or something else to hide your pump this division probably won't be necessary anyway.
Next, you probably want to use some substrate between the mesh and the moss that you can grow plants in. Having all moss doesn't provide many hiding places or variety and moss can be tricky to grow for some. Also, this will provide more drainage for your enclosure and allow you to provide some "terrain".
Finally, if you are able to do so, drill a drain hole (or have one drilled) and put a bulkhead in there. I didn't do this and wish I had. Siphoning water is only fun the first time and getting a mouthful of vivarium water isn't on the top 10 list of things I like to do.
Good luck, keep us posted, and welcome to the board.