The obvious answer to the glowing materia conundrum is a milky/phosphorescent swirl mix in a pale green orb (starting with the white materia here). To make it glow you could coat it with photovoltaic film (you can get a resinous version), then have a small LED inside the orb with a more solid coloured core to hide the gubbins. Don't make me think any more than that ATM, my brain hurts - but it does negate the need for batteries and most of the wiring that goes with it.
EDIT: I'll have a go at costing it later, this might be something a 3D printer would cater for perfectly.
I've read all the way through the thread in one go, there's some amazing ideas in here. I'm still after a TLS logo t-shirt/hoodie.