Decided to completely replace luck as a stat because it didn't do anything, so it's now "spontaneity". This is effectively a speed modifier on all actions, any time an action is taken all speed is recalculated with spontaneity as the upper bound in a random value.

So say you have a base speed of 16 and a spontaneity of 5.
The battle starts, a random number between 0 and 4 is generated.
You get 2.
Your speed is now 18.
Enemy has speed of 19, they get the first turn.
Your speed is recalculated, you roll 1 this time.
Your speed is now 17.

You take an action, recalculated again.
You roll 4, speed is now 20.
The full turn ended, so it's now the next turn - you have 20 speed, enemy has 19.
You effectively get two turns back to back here due to how the turn ended.

Very basic example, some fun stuff can be done with it. Also, you know full well I'm going to add a rare encounter with an enemy that has high spontaneity. Good luck trying to plan around an enemy that constantly changes its position in the turn order!