Peacock Mantis's are by far the most prettiest mantis. They are however, one of the biggest, and can reach almost 12" in length (you probably know this already).
Eventually, you can keep corals if you ever want to. Mantis's rarely touch corals, and if they do, it is not lethal.
Actinic Lighting would definatley make a Peacock pop. You will want that, but with a decent daylight 10000k bulb. You may also want to invest in some moonlighting (either blue or red) to see his predatory actions. The Depth is what I would be worried about... How long is the tank in the front? You may have to hang some sort of light system to make sure the light gets everywhere.
If I had to recommend some cheap, but good lights for a FOWLR, then I would suggest this: Compact Fluorescent Aquarium Lighting: Single Satellite Compact Fluorescent Fixtures
I like your plans for filtration. You will most likely need more than one powerhead to sustain enough turnover (Your looking for at the very least, 20 times turnover. IMO, 25-35 is ideal). Koralia Powerheads is my favorite.
For your CUC, I really wouldn't even bother having a full-on crew. A "good" Mantis can wipe out any decent CUC in a day or two if the shrimp wasnt a hitchhiker. Most Mantis's are fine with like a hermit or snail being dropped in every day/every other day (for small ones), and as they get bigger, you can introduce crabs.