Hi Maria - No need to tell you that I am a great fan of you. Think that you could dominate the tour, here are a few proposals to further improve your game, for your consideration.
(1) 100% execution of "high emergency balls" of your opponent bouncing directly behind the net
Non-execution cost you the win against Radwanska in Miami at breakball 3:3 in the second set. Her ball was in the air for at least 5 seconds. You preferred to await it and shoot it cross-court with your backhand, as you always do. In 80% of the cases this is enough but not in exceptional situations as the one mentioned. Your "execution" with the backhand is not the 100% killer, rather foreseeable and therefore has cost and will cost you further matches if not changed. The, seemingly, easy solution is: run around the ball, await it with your forehand (even with standing in the "corridor" for doubles if need be), change your grip to shoot it totally flat and hammer it onto your opponent's t-line so that it bounces into the audience. Any mediocre tennis player is able to do this, so it should also be possible for you. In order to not be misunderstood: I do not talk about smashing it, rather a "normal" forehand shot, however flat and without any topspin (that presumably is the problem for you). But I am only talking about hopeless balls of your opponent where you will have all the time to find your position and change your grip.
By the way, a similar unability to execute cost Martina Hingis two or three Grand Slam finals against Davenport and Williams: She always used her forehand but with a ridiculously lame topspin shot cross-court that again was good enough in 80% of the cases but not in extreme situations where the opponent doubled her efforts, ran like hell and got to shoot a longline backhand winner.
You will need said execution shots a lot on clay, thus in Roland Garros: Maria, I really want to see you run around to your forehand and hammer the ball - flat - into the empty court of your opponent.
(2) Smashes - You never smash, and my guess is that it would not be healthy for your shoulder to do so, then it's okay. But otherwise I would recommend to try smashes in the way of Martina Hingis, namely by always slicing them (heavily) with the forehand. Is usually enough to make the point, is relatively safe, do not target the lines but rather smash into the middle, usually causing enough wrong-footing. The "volley" topspin shot you are always using (you do it quite well) is not that easy and often is not fast enough to end the point.
(3) When dominating an exchange, targeting the same side ball after ball - All your opponents know that you like you play, after a firing forehand cross-court into the backhand, another forehand cross-court and so forth. So, there rarely is any wrong-footing, nevertheless you often make the point sooner or later. But against e.g. Radwanska it was obvious that you had better options: (a) often her backhand was left alone that much that a shot into that direction seemed advisable. Fast, but no need to go closely to the lines, with going to the net and be prepared to still play an easy volley if need be. (b) Play more angle with your forehand to her forehand when being a yard inside the baseline and dominating the exchange.
This is of course dependent on your opponent. Wosniacki, for example, likes to run from one side to the other (at least on clay), there playing "same side" is often advisable.
(4) At least against top players, you have to take early offered easy games, you cannot afford to donate all said games - These are typical situations in your game: Azarenka in the Australian Open final is nervous and has 0:2, 0:40. Or e.g. third set against Justine Henin in Paris 2-3 years ago, where she was back 0:3, 0:40. Of course, I know you are playing point by point and did not deliberately lose these extraordinarily important games. But my impression is that you have not yet switched into "high alert big point mode" in said early situations, what you should do, however, to secure the games. This concretely means to avoid easy errors, shorts which are wide by a yard or so. I think you are very well able to switch into said mode but only towards the end of a match. Against top players, it may be necessary to do it early, at least if a 0:40 opportunity is there. Against Radwanska in Miami, a similar situation arose in the first game already (where you had elected to receive, as usual): You errors after 15:30 were massive.
Let me stop here and see whether you and the Forum is interested to discuss this any further.
All the best and kind regards,
Leopold2