1. The running: Allow the players to change directions when having decided to do so...
Allow the player to run around a backhand to hit it with his better forehand. I manage to do that in TS3 only in about 1 % of the cases in which i wanted it. Therefore, the running speed should be greatly improved.
2. The shot-control: Allow a player to hit more than once per incoming ball! Its so ugly when u pressed a wrong button shortly and involuntarily and then watch an "ultra-noob" ball simply bounce past you in slow-motion, even if you had enough time to walk backwards towards the ball.
Create a true analogue aiming, where pushing the analogue stick 100% in a direction will amost always result in an error. Remove the option to press left trigger to be able to hit the lines altogether, precision should come from the player that controls his avatar, not from some auto-aim in the game...
Sometimes, even only rarely, the ball should hit the net and roll over it
3. Bring the analogue triggers to a greater use. I could imagine analogue adjustment to ball power, or the amount of spin thats in a given ball.
4. I am not a fan of having to challenge balls. I think its a luxury that should stay in tennis games, that there are no human misdecisions.
5. TS4-TV additional idea:
Let the players be the audience. Imagine how cool it would be if you`d play a major tournament match, and the spectators were only players with their avatars, trying to analyze your game or enjoying the show. They should also get the choice to interact a little, maybe by applauding, cheering, la-olaing, giving standing ovations or the like. I am bored of the cpu spectators
6. The equipment: Give the full Item description with all modifiers to stats and abilities that the item really offers. Then, more items are better than less! (thinking of free DLC)