[Lord Carnifex]

I'm a little confused. Let me see if I understand the problem here.

Currently, the turn order in most combats is "Knight - Wizaed - Badguy"

and you'd like it to be "Wizard - Knight - Badguy"

or are willing to settle for "Wizard - Badguy - Knight"

right?

If you're willing to settle for W B K W B K W B K W B K..., why not just pick a relatively passive maneuver for the Knight's first turn, like All-Out Defense, Evaluate, or Do Nothing? Doing so would effectively change (K W B K W B K W B...) into K (W B K W B K W B...) which would seem to get you what you want.

Remember that spell durations and other intervals are judged from the one Wizard turn to the next Wizard turn - A spell with a one turn duration might take effect at the end of Wizard turn 1 and will last until the beginning of Wizard turn 2, effectively giving the Knight a turn between them. Thus if the spell casting is W* and the spell ending is #w, then the turn order with a one second spell might look like:

K, W* (casts spell), B, K, #(spell ends) W* (casts another spell), B, K, #(spell ends) W*, and so on. Each second of the spell duration, the Knight will get one turn to act.
...
If all of that is too complicated, and I were your GM, I'd probably allow you to declare your position in the turn order as any number less than your Basic speed, up to a maximum of your basic speed. The way I'd do it, you'd select your "effective basic speed" as the combat starts, but before anyone takes their first combat turn.

I don't see this breaking the game dramatically.