One note before I start: Don't double post, edit your post instead by pressing the "Modify button".
The system is fairly easy, but it could turn out quite big. The most important piece of the minigame is timing keys. i.e. you have 10 frames time (20 frames = 1 second in event) to press the down key. During that time an image is displayed showing the button. You can put in any image by using the "Show Picture" event command as I will make script that will handle the images because I use custom controls which you can set up to your own needs. In any case, here is how the system works:
The game starts with 2 ratings of 1000, which is 100,0%. For each mistake the player loses a different value, i.e. 1% for a missed dialogue, 2% for a missed key action, etc. of the first rating and 1% of the second. The player gets 1% for each successful action on the first rating, but NOT on the second rating. The second rating acts as a limiter for mistakes. The first rating can't be higher than the second one, in other words, even if you make mistakes at the beginning and do everything else well, you can't get a 100% rating anymore.
There are several situations where the player can get in:
1. Dialogue; the player has to reply choose the right text. This is also timed. If the player doesn't respond in time he loses points.
2. Moves; the appear during the dialogue scenes. Here the RIGHT movement is being executed regardless of what the player pressed. Incorrect key presses descrease the first rating by 3% and the second by 1%.
3. Battle A; the player has to attack. Each button that is triggered in the right period of time (what I described in the beginning of this post) will execute a different attack. The other fighter ALWAYS counters/dodges correctly the player's attack, but for the wrong attack the player will loses 2% on the first rating and 1% on the second (as I said described already).
4. Battle B; the player had to counter/dodge attacks. This works the same as Battle A moves. The importance why there are 2 different battle types is that there can't be more than 3 different moves of one battle type in a row. i.e. 3A - 2B - 2A is ok while 3B - 4A - 2B isn't.
Each key input uses another set of buttons. i.e. movement can be the normal movement keys, attack can use ENTER, ESC and SHIFT, while the attacks use X, Y, R and L buttons.
You should create common event calls for the different things that need to be executed. You don't need to create any scenes that use this minigame system, I will take care of that. Of course you will have to create one scene for yourself to be able to test it.
Still think you can do it?