Here's some more:
4. It would be good if long-prepared shot gets accuracy & speed bonus, for both players and CPU.
I don't mean quality of shots should mainly depend on prepare time, like VT3. I just think it reflects the reality, and helps offensive player expand advantage, shorten average ball length, as you planned.
5. About the player attribute system
In TE2013, different attributes already weigh differently. Some cost higher on each point when already at high stage, but the value is not balanced yet. Here's my personal opinion:
Fitness (stamina & speed) should have the highest value, since it influences the effectiveness of almost all other attributes;
Counter ability deserves more value. It's one of the cheapest atrributes now, but it really is one of the most useful ones, since it increases both speed and stability of all your shot in a high-quality match;
Top Spin, as a special attribute that doesn't cost points, the higher it is, the slower your shot will be. I assume this is designed for balance, but it really reduces aggressiveness of players with high top spin value. Top spin shouldn't be on the opposite side of aggressiveness, Nadal says.
Top spin even affects slice speed, that's another problem. I think there could be another way to balance top spin, like you could add the possibility of returning the ball into the net when using acceleration, and the possibility depends on top spin value.
I have a question about Lob: what's the difference between defensive and aggressive lob, except for speed? because in my test, their speed don't have significant difference, yet defensive lob costs much less stamina, and has better stability. If the aggressive lob was designed to do winners, maybe you can add some top spin in it, so that it will accelerate when hitting the ground, making it harder to reach. The level of this top spin doesn't depend on "Top Spin", but on "Lob".