First of all theres no need to hold RMB to move racket, just move it with mouse and it will be 50% more playable.
Also theres needed a fullscreen mode to test and adjust table and ball sizes.
I think circle rackets are not the most comfy option to start, im suggesting to make a normal vertical rectangle racket and control the angle of it by MouseWheel and/or LMB-RMB (racket spin needed to be smooth, not instant angle change if possible).
Additional controls that might be needed in future:
- camera size adjust (W-zoom, S-unzoom)
- return racket in vertical state (SPACEBAR/MMB)
For tests would be nice to have adjustable physics options before the match:
- racket-ball bouncyness
- racket spin speed
- racket friction/ball spin multiplier
- racket-table-ball size
When ball is out of screen, a dynamic edge indicator will help a lot (further the ball from edge - smaller the indicator).
For online matches there might be needed a racket speed limit for balancing.