To take the power and subjectivity out of the umpire's chair, I suggest the following to give the players the control of the match tempo in regards to the Shot Clock.
Once a point ends, whichever player steps into position (server or receiver) the clock starts for the other player to get ready. Give the other player 15 seconds after the original player takes their position.
This way if the crowd is cheering loudly no one steps up to the plate until it cools off, or if they played a long agonizing point they might wait to take their spots (or the fitter player might get on the sport right away to the detriment of the other player). With aces, the server might just step over and then the receiver only has 15 seconds to get back in place--no need to towel off and walk to the back wall. Players might become more selective when to go to the towel.
Hence, either player could get a warning and possible penalty for not being ready after the first player takes their spot.
Once a point ends, whichever player steps into position (server or receiver) the clock starts for the other player to get ready. Give the other player 15 seconds after the original player takes their position.
This way if the crowd is cheering loudly no one steps up to the plate until it cools off, or if they played a long agonizing point they might wait to take their spots (or the fitter player might get on the sport right away to the detriment of the other player). With aces, the server might just step over and then the receiver only has 15 seconds to get back in place--no need to towel off and walk to the back wall. Players might become more selective when to go to the towel.
Hence, either player could get a warning and possible penalty for not being ready after the first player takes their spot.