Flash had a bit more going for it/incentive to reverse engineer not to mention based one some more known methods.
VX being shared across many games means you can probably find a game to inject your video into and grab it there. A similar method is used by the presently best SDAT ripping methods (caitsith2 and snakemeat's stuff) so it does work- desmume has a rather nice video grabber these days.
My usual example as to why nobody has reversed it yet is to point at
http://www.cmlab.csie.ntu.edu.tw/cml/dsp/t...g/coding/mpeg1/
pixels (2d graphics) are just that, compression is usually based on some known method (LZ, huffman, filtering or RLE) with simple concepts, animation can be a bit tricky but still nothing major.
3d graphics are not that much harder- you have key frames and you have bones. Textures and light are not that bad once you understand the underlying stuff
sound is usually some form of wave/PCM + wrapper.
levels are usually static.
text might get fun but again it is static and easy to toy with.
game logic is plain to observe and ultimately control
and so on for all the areas of rom hacking (not saying it is not complex on occasion but all have large things that help it out) but video as you can see from that link is a nightmare and that is something as old/basic and common (video (software) patents make for some interesting ideas) as MPEG- about 20 years old at this point in time.
Also as for grabbing it from the SDK (not that you mentioned it but many people head here next) I am told it is locked down above and beyond what the main SDK is.