Well, simply because I love coding on PS2 and this sounds like a fun project :)
Also, because this would let me put my PS2 in the cabinet for my own homebrew development with zero special hardware, it would be really cool to have a truly "JVSised" PS2 sitting in the cab talking to it just like the NAOMI does. (In fact, I think there there is a PS2 based JVS arcade box which does just this via USB - quite cool!)
Plus, I can output native VGA 640x480 from the PS2 just like NAOMI does, so it would be a quite cool platform to do homebrew arcade dev with, and intergrate "properly".
Also, the cable I was talking about was this:
http://balthasar.neovanglist.net/PlaySt ... ACable.jpg
(Note it's even official :)
This only leaves the power connection, which is bog standard AC current.
Much nicer than a dodgy PS2->JAMMA then JAMMA->JVS solution I think... (And way more fun to work on :)
Also, I found the official JVS standard PDF, which includes the USB communications protocol:
http://www.jamma.or.jp/siryou/siryou02/JVST_VER3.pdf
I'm having a friend who knows Japanese look into translating it now... maybe I'll have to take a couple days vacation soon to look into this!
Also: Just realized that during the development phase I would probably write the first driver implimentations in FreeBSD for testing - This could be ported elsewhere and be quite cool for setting up MAME boxes or other PC-in-cab things so that you have an actual driver for the JVS interface and don't have to buy extra hardware or special jamma stuff.