I built a splitter box with a few switches. We had 2 joysticks hooked to the box. The driver could configure it for 2 joystick drive, or 1 joystick drive and even select which stick they wanted to use. I did that in case we had joysticks that weren't ambidextrous (but we ended up with the 2003 flight sticks, so it didn't matter.)
That way the driver couldn't complain they didn't like the control setup, because they could switch it on the fly during a match.
For the arm operator, (me...) I had a project box with a db-15 cable coming out of it. It had a double momentary ( (on)-off-(on) ) switch for up and down of the arm, and a pot to control the speed. Most of the time I left the speed all the way up, but it was easy enough to turn down for when I needed to be gentle. (not that often
just putting the arm away)
I also had other switches on the box for our unfolding hook (that didn't work and got replaced with a fixed hook) and our latch to keep the arm for back driving, (which really wasn't needed so it was taken off) and selection of our autonomous mode, (I never got the selection working, so that was never needed either. I just left it on our "good" mode)
The driver drove, and had nothing else to fiddle with, and the arm operator did all the arm stuff, and I would have to say with a good team, we worked fairly well.