I have the schematic finished, and I'm working on the layout of the board.  The board has 4 sides, so each port will get its own side.  For the serial port, I plan on just having 6 pins soldered on the top of the board.  That one will plug top-side into the serial port instead of the dongle.  There's hardly any assembly needed.  

I have to make sure all the boards will fit together when plugged in.  So I printed out four to-scale boards and cut them out.  I placed them next to each other on the back of my C64.  The only problem board is the serial port.  The board is too wide.  It hits both the video port and the cassette port.  BUT I think I can make it work if I turn the board 45 degrees.  This looks kinda weird, but if it works, then it's not wrong.

I'll get a rendering going here tomorrow.