I'm working on a solution to what I think breaks the entire concept of sequence: surprise turns.
Right now sequence works like this: the combat initiator gets the first "surprise" attack, then the others, and for the following turn, the one with the highest sequence gets the first attack.
What this means, is that in a fight between someone with awesome reflexes (dude A), who initiates combat, and someone with crappy reflexes (dude B), combat turns progress like this: A, B, B, A, B, A, B, etc. Who has the advantage in this situation? Clearly depends on the chance of killing someone in the first round (A has the advantage) or in two rounds (B has the advantage), but on the whole this is about even, which defeats the entire purpose of having awesome sequence: what most matters is who starts combat with a "surprise" attack, even if it isn't actually a surprise.
I want to fix this by making a "surprise" attack, an actual surprise: if your target (the one you're aiming your weapon at in the first turn) doesn't see you, then everything works as normal and you get your surprise advantage. If, additionally, you have higher sequence than the opponent, you also keep your second turn advantage, so turns progress A, A, B, A, B, A, etc. If you have lower sequence, then you lose your second turn advantage, but now so does the enemy (in practice this means that his sequence gets lowered to 0), which means that turns progress A, B, A, B, A, B, A, etc.
However, if he does see you, then one of two things can happen:
(1) you have higher sequence than the enemy, which means you "keep" your first turn, but "lose" your advantage in the second, so turns progress A, B, A, B, A, B, etc.
(2) you have lower sequence than the enemy, which means you lose your first turn, but the enemy loses his advantage in the second, so turns progress B, A, B, A, B, A, B, etc.
Long story short: who initiates combat won't be important anymore, unless it's a sneak attack that the enemy (and his team mates) don't see coming.