Also, for reference, Wangan Midnight is actually the SECOND game in the series on the 246- the first is Wangan Midnight R (and yes, it's the first, even though it's 'R', I promise.) Both games shipped with the same 246 'driving' chassis as RRV, BUT word is that they have a larger drive cache RAM card than RRV. I'm still on the lookout for one of these larger cards, but the game's booting seems unrelated to this card.
In addition, Battle Gear 3/3 Tuned are separate games, although the original cabinet appears upgradable. They have separate dongles, HDD's, and a separate NM0000XX ID. They also have IC card capability by way of 'keys' that presumably have RFID chips embedded in the plastic of their key fob, but I haven't bought a proxmark3 yet to poke around with them, and I only have ONE... If anyone knows where to get more- even used, please let me know! An interesting thing is that we long thought BG3/Tuned needed a SPECIFIC Taito 'JVS IO PCB' board, but it appears that the game hangs at boot if any of the analog inputs are left floating, unlike RRV and WM/WMR