Stronger magnets means more voltage at a given RPM. So you can go to fewer turns of thicker wire to keep the same voltage and get more current (and more load torque).
Thicker magnets means the optimum gap is wider, letting you put a thicker coil in, stuff in more copper, and pull out more power. (Gap should be about equal to the sum of the thicknesses of the magnets on either side of it.) Again you can use thicker wire for more current (and load torque). You'll have to adjust the number of turns for the actual field in the gap - it just got more complicated when you changed the gap so it's not a simple expression.
Of course you need more horsepower from the turbine to produce more watts. So you need longer blades (unless the current ones are in stall). The optimum TSR remains the same but the circumference is greater so the RPM is lower, which lowers voltage, which needs more turns...
So you need to do a bit of algebra, and maybe build some trial coils, to adjust the design.