Wow, nice elaborate construction, and I simply love anything that lights up.
Further distressing/aging will definitely take it up to the next level.
For putting dirt and mud splatters on your hard armor pieces, I had good luck with a little batch of Monster Mud, which is a homemade mixture of about 3 parts drywall mud and 1 part paint (latex or acrylic) - it's very popular on halloweenforums.com. It will dry nice and hard, though it still may shed a little bit of grit and dust, and it's definitely not waterproof. It won't be easily removable/reversible, especially once it's dried.
Also, a dilute paint wash will help to age/distress the hard pieces further. Mix up some black/brown acrylic paint with lots of water so it's very thin, and spritz/sponge/wipe/pour it over the pieces. The dilute wash will collect in any crevices and really give it depth. If you've done any miniatures painting, you're familiar with this technique.
I don't have any good advice on distressing/dirtying/aging the cloth bits. I'm going to embark on that within the next couple of days to get my costume wrapped up in time for Dragon*Con. I'll update my construction thread once I have made more progress there.
For an example of the Monster Mud, see how it looks on my WIP helmet here: