Update:
I actually did the both the cable and clean versions. Both worked well. The clean version looks much nicer and is better with the totally clean version that I'm going to present now.
First, do the JST XH 2.54MM 9 Pin Female option. The USB cable only has to be about 4-6", when done.
Then order these:
(1) USB Splitter 1 in 3 Out
https://www.amazon.com/dp/B0GH45DKS7(1) USB 3.0 to USB C Panel Mount Adapter Connector
https://www.amazon.com/dp/B0GH45DKS7(1) JST EH 4Pin (JTS-2.5-EH) connector (I can't find smaller EH set of connectors that aren't in a set like these)
https://www.amazon.com/dp/B0F2MDCCQL(1) Nylon Hole Plug Set
https://www.amazon.com/dp/B0DKFHDWVYRemove the track ball by unbolting it from the tankstick. Don't lose the nuts.
Remove all four screws holding the trackball together. Don't lose the screws. MAKE SURE YOU ARE HOLDING THE TRACKBALL CASE TOGETHER AFTER REMOVING THE LAST SCREW SO IT DOESN'T DROP EVERYTHING ON THE FLOOR!
Flip the trackball case over and remove the top. Now is a great time to clean the trackball and all it's parts. It's amazing how much hair gets in there.
Grab the USB cable and carefully remove it from the grommet and circuit board. Why they chose to use JST EH connectors instead of the more common JST XH connectors, I can't explain.
Now connect a prewired USB cable to a new JST EH connector, following the color scheme on the old connector (Red, White, Green, Black, on mine). This USB cable also doesn't need to be more than 6" long.
Once you've verified your new trackball and joystick USB connections work independently, connect them both up to USB splitter.
Now drill a 1" diameter hole somewhere on the back of the tankstick. I chose the middle, but you do you.
Screw in the USB 3.0 to USB C Panel Mount Adapter Connector in the hole you just made, and connect the USB splitter into that. Now you have ONE USB C connection for the trackball AND joysticks.
Don't forget to screw everything back together as you took it apart, and wire tie all the loose wires.
Now you can use the nylon hole plugs to cover the empty holes left by the old cables.
If you choose to be forward thinking, you could use the extra USB port to power LEDs inside the tankstick, or dangle it outside for a keyboard connection.
Have fun!