Hmm... heres a few ideas I thought up that some may find helpfull...
Have the 3rd and 4th players use control pads that dangle off the sides. If you think about it... there arnt that many times when you have 4 people over that want to play a 4 player game... and even if so... they probably wouldnt care if they had to take the pads. Besides, those 4players dont need as much accuracy as say... the 2player fighters. (not to mention... you might save some money and construction time) ((altough, if you dont have 2 sets of close sticks... robotron or smash tv wont be very fun))
Next... is the idea of a 'fold-out' trackball panel. Basically, attach a 2nd smaller controll panel (dual trackballs - and spinners?) to the front of the original control panel using door hinges.
The panel would hang down in front while playing fighters... and then just make a simple prop-up/locking mechanism, and its level and ready to rock : ) The great thing about it is that there is nearly no change over time, no cables to connect/disconnect, no clutter, no reaching-straining or fumbling arround other controls to play them : )
Finally, something that I havnt seen dont yet either... is to say... mount devices on swinging arms (hinges again
on either side of the cab. Steering wheels would probably work very well for this.
One of my other older ideas was also to make telescopic surround speaker holders. Basically, take 4 pipes (2 larger pipes, and 2 smaller ones that fit inside the larger pipes) and mount them to the top of a cab. Then, mount hanging speakers to them. You can have them behind the players so that the sound is more realistic and also, no wires to trip on... or external mounts elsewhere. Simply slide (retract) them twords the cab when done... to make it look nice when not in use. : )
What do ya thinks?
Peace