It is easy for us to say: "it would be good IF..." But bottom line that has to follow with a relatively simple way to execute it, at least it should "sound" relatively simple.
As far as serve, read my comment above. I agree it would be great. But, for it to work, they have to include more variable. At least one more to the existing 3. Now it is either in, out, or net. They will have to add another timing window on your "direction hold" that will allow for Let-go-over the net to happen. This means that it is a set value....like 0.52sec hold time (example) - that in turn means it is not random and can be (make it will be) exploited. How? ....I can just imagine a 12 y/o kid doing lets 4-5 times in a raw just to annoy you.
So then the random option right? ...I doubt that you, with your timing, will be happy when AI decided to take away a point or two from you in tie break. ....and have you seen how many tie breaks we have it ITST? ....that essentially will mean that most of our matches will be decided by Random AI events rather then our game play.

So no thank you. When it concerns Lets/Nets I rather have NONE that any of the two scenarios above.
Now as far as hitting the lines during rally or serve, that is actually relatively simple. We essentialy hitting lines now...it is just that the lines positioned wrong. They could have set the "close to the line" value as "on the line" value and wallaa! But the key still, we have no control of that. AI decides between certain amount of values and attributes this values to chosen shot.
So essentially we back to square one, if you make another value...then we will find it and exploit it. Random again?

See what I mean?
We need a drastic solutions, not wishful thinking. Hopefully TS4 can deliver these, rather then try and do what we do and improve the existing engine. I think it is running at almost capacity and they need to redesign a nice part of "how" the ball placement relates to other buttons to make it work.