Combining Defender and Robotron on the same machine is not a trivial problem !
1 Control Panel, 2 Sticks:
This is a commonly found design because there has been a control panel overlay and multiwilliams game boards available for a long time. It uses 2 grommet sticks (eg Wico).
We judge this panel as not very appealing, it adds a poor Defender experience to a Robotron panel. Much better value could be achieved by adding more buttons ( ie a fighter panel )
1 Control Panel, 3 Sticks:
There are two feasible layouts for this.
The symmetric layout has Robotron sticks set closer together, and Defender controls set wider than standard.
The offset layout has both sets of controls with the standard width, but offsets Robotron to the left and Defender to the right. This layout allows for 2 player Joust.
2 Control Panels (3 sticks):
This is why we designed the swap panel system, the point of this option is that you can have both Defender and Robotron with the correct controls in the standard positions. Also you can have both sets of original graphics. And beyond Williams, you can add other control panels too.
This configuration adds some cost due to the extra panel, and possibly extra storage cost. Panel swap-over is quick, but not as quick as just having one panel.
Your Multi-Williams could be based on any of the cabinet styles: LowBoy, Williams, Defender.
Graphics can be tailored in a wide variety of ways. You can choose two different side arts. You could choose an overall colour scheme eg Red/Yellow or Blue/Yellow and apply that to all the panels and sides. Or you could keep each panel to its own standard colours.
With the swap panel system, the marquee is also quick swappable so you can have one to match each panel.
Add a specific Joust or Moon Patrol or Sinistar control panel if you want more Williams goodness.