Fred i dont think he wants to alter the impedence. Impedance is the sum of all connected parts. If only the tweeter's ,mids and associated crossover parts are seperated from the woofers ,the overall impedance seen by the amplifier would change.If someone was to run 2 wires from the same amp ,the impedance seen by the amp would remain unchanged. I will run some impedance sweeps on my M80's tonite and see what the difference is.
As can be seen here,takeing out the bridgeing would result in two seperate crossovers.