You know awhile back I purchased some small rectangular yellow LEDs for MG's eyes. After I saw your new product listed, I figured I should probably disassemble my MG & get to work on modding mine.
It wasn't very simple to remove the toy. Lots of odd angles & tiny screws to get at, but I eventually got the coil pulled, the hinge screws off & could remove the toy. I was surprised how dense the MG toy is, as I was expecting it to be much hollower inside. It's almost like a solid piece with a small cavity inside. The skin isn't thin, so drilling the eyes is no simple task. The MG head is very dense, and it might be difficult to drill the eyeholes at a good angle to hit the cavity space to run wires inside. After looking it over, I decided my idea (with micro sized LEDs & TINY wires at could break with constant bashing) just wasn't worth the effort.
But if someone really wants to light the MG eyes, then I feel your product is the way to do it. Your diffuser splitter & optic tubing is the right design, as it looks robust, easy to hookup via Matrix wiring & should be straightforward to feed the tubing into the holes. Drilling the eye holes would be the hardest & most crucial step.
If you release a PDF with detailed install steps & close up photos of each step, you'd probably sell more of them. Good luck!