Suits, the only thing wrong with your cab (and I say "wrong" in the loose sense), is that your panel was unnecessarily huge. The rest of your cab is fine - quite good actually. There's no need to rebuild that. Just remake your control panel (and rig up wires so you can swap it out if you want additional controls) and you're set.
The one thing about 4-player panels that makes me discourage their building is that people seem to overestimate the amount of space required for the outer players. This leads to ridiculously wide CPs and the dreaded "angling" of joysticks (contrary to popular belief, a player can stand off to the side of the panel and more than adequately work a joystick oriented relative to the screen - see: Gauntlet). My advice to you is to take a look at some 4-player cabs on klov.com and notice how they do it and keep it simple.
As for the two-piece design, take a look
at this thread before you commit to it (#1). But I still say that you leave the cab's body as-is.
