Well, the 8 buttons are very easy to explain.
Console 4 player games.
SNES had some awesome 4 player games (pretty much invented the multiplayer console games). N64 was the king of 4 player game. While N64 hasn't been emulated to the fullest extent, SNES has so I wanted to have my CP ready for it.
For me, SNES was the height of the gaming, and since that time it hasn't been the same

. While my cab will have arcade games, most of the games on there are SNES games.
Eight buttons might be excessive to some, but come on, I've seen alot wierder things than that on CP's. (Don't make me have to link to something cuz I will

)
Dedicated four way....hmm...well since my CP is removable I can always create a second CP for that. Like a said above SNES was more my
golden age of gaming, so I had to keep my priorities straight.
8 buttons also gives me some flexibility to add newer consoles in the future if'n the emulators ever reach as good of state as the SNES/NES/Genesis/Mame emulators.