Woodrow, I know. My UF employee Example was that the calls shouldn't be made by players. He wasn't a fan of the honor system. His reference to volleyball was that they do have line judges that make the calls, not the players. I pointed out to him that it would be a cost and logistical mess to have every line called in tennis.
My point is, even with an up umpire and down official, there would still be calls on the baseline and service line that neither are standing on and don't have a direct line of sight to see if a piece of fuzz actually touched white paint. In volleyball, the line judges can call 2 lines each and don't have a service line to call. They are standing right on the corner of baseline and sideline.
I too like the current system of players calling and officials only over ruling. It is economically and logistically unfeasible to add officials to a sport that rarely charges admission.