I had no idea how much wiring was involved.

Drawings on a diagram don't look as complicated.

After thinking about it for quite some time. I decide it was possible to build a controller that can work with the 2600, 7800, and 5200.

The photos show one controller wired up using 4 x 715 i2c chips (8 switches per chip), 1 x 5242 i2c chip (two digital pots per chip), and a gpio controlled mic chip for controlling power.

The final version of this thing, that can effectively control both VCS/7800 ports (all controllers) and 2 x 5200 ports (basic controllers). That version will require:

8 x 715's, 2 x 5242's, 1 x i2c multiplexer, and 1 x mic chip for power.

I own a 4 port 5200, but having a version that could control all 4 ports would require almost double the chips:

16 x 715s, 4 x 5242's, 1 x i2c multiplexer chip, and 1 x mic chip for power.

I think I need a coupe of days break from this.