interesting concept! i love games that combine sports with moba/class elements uniqely.
have you expirimented with a longer court? i feel as though that small adjustment would greatly benifit the pace of the game. also, pasive abilities unique to a champion would be a concept i would like to see implimented. a little more polish and *maybe* some voice lines and i would start paying for the game!
an example for a pasive ability could be simple, like the size of the charector's hit box (wich youve already done) but others could be different. for example, the charector's special could slowly charge over time whereaz onother charector gets slightly faster if he gets a certian amount of volleys in a row. i also have ideas for new powerups if you are interested