I'd like to first say I really like this game, it's by far the most realistic tennis game. I have some minor things though that I haven't really seen talked about that I hope won't be in TE4 or that could be improved in TE4.
1) So I played real competitive tennis for more than a decade and the one thing that kind of bugs me in this game is linesmen calling out when I hit a serve or regular shot in the net, they don't do that because the ball isn't out (there is no call needed when the ball hits the net you just lose the point).
2) Also the umpire calls let when I miss my first serve into the net which also isn't correct it's not a let it's a fault and the umpire doesn't call fault (unless it's an overrule). Lets are only when it clips the top of the net and lands inside the service box. I feel like having these wrong extra calls not only isn't realistic but it's also a bit of a nuisance for casual players who don't know about tennis having to hear all that for no reason.
3) My other gripe is net play, I feel like it should be easier to pass when the opposing player is at the net and easier to finish points when you're at the net so it's not a rally. I understand it's not hard to pass on the approach but that shouldn't be the only way to pass on higher difficulties. I find that once the computer is at the net the only way to pass is cross court with almost perfect accuracy near the opposite alley line, passing down the line is practically impossible. I also feel that power on the shot should affect the computer's ability to volley, with time to load up your shot it should be much easier to pass as we see in real tennis because the volleyer can't handle the shot's velocity. I also feel when I approach the net I have to sometimes hit at least 2-3 perfect volleys to win the point. Like I'll hit a volley to the far right corner and then the far left corner and the computer player can still get to it. I feel like the pace/speed on volleys should be increased so it's more coming to the net to finish off a point like in real tennis rather than a cat and mouse game (smashes need a boost in speed also imo).
4) Another thing, I feel like lobs and drop shots should be more useful. I don't think they should have a perfect success rate by any means but I think a higher success rate would add more variety and realism to the game. I don't use the lob at all because it almost never works on higher difficulties, same with drop shots unless I'm way inside the court and the computer is well behind the baseline and even if that, some fast computers players can get to it quite easily.
5) Last thing is game adjustments, I don't know if there is a way to adjust serve position for the computer. I always found that serving from the deuce side with a right handed player it's way easier acing down the middle then out wide. It isn't the case on the ad side because the computer's return position is more neutral where as on the deuce side the return position is covering more out wide. I tried to see if I could adjust the computer's return position in the game files but couldn't find it. Obviously it would be really difficult to program but it would be cool to see AI make adjustments based on patterns, like if hit multiple aces down the middle they could cover the middle a little more or if I hit out wide they would cover out wide slightly more (they would have to make that adjustment during the serve motion or else I'd be able to see it).
6) Same thing on their serve, I tend to cover out wide on their deuce side because that's mostly where the AI serves to and down the middle on the ad side. It'd be cool if they made adjustments based on your return or maybe mix their serve a bit more evenly. However, if there is a way for me to change return position on computers manually please let me know I'd love to experiment with that.
7) Something cool for the future would be introducing animations for hits on the run when the player is fully stretched out to hit an aggressive hard desperation shot, and make them risky but rewarding. I think that would be very hard to implement in any tennis game especially with this game but maybe something would be cool down the road, I don't know the limitations. That being said, thank you very much for this game it's the only playable tennis game imo and I'm very excited for TE4!