Bi-amping + speaker crossovers = redundant?

NO! The crossovers determine how much power each section of the speaker gets, if you have no crossover the tweeter and mid gets as much power as the woofer, a sure recipe for disaster. What you are looking for is an external electronic crossover which attenuates the signal before the amp sees it. You can also remove the crossover from the cabinet to improve the sound. Even if what you propose was possible the amps would require rebalancing every time you changed the level.

This will get complicated as the electronic crossover will have to be placed between the signal source and the two amps if it is to divide the frequency between them. I am having a little trouble visualizing the exact configuration and I have a fairly complex system. The signal cannot pass through the 'Master" amp to the "Slave" amp as it will not be the full range signal, only the partial signal. There is no way I know of to place the crossover between the amps and the speaker as it acts on the signal, not the amp output. It will feed two separate signals to the two amps and you are back with two volume controls. There is a reason why, despite their many drawbacks, almost all speakers are passive. KISS rules again!

OK, I finally thought of how it would work. Signal to one pre section, then to the electronic crossover , the signal is split and the level balanced with its volume controls, then out to each of the amp sections, not using the second pre stage. But you will still have the problems Drew described. Last winter I considered something like this; I have 6 identical mono amps and speakers that are tri wirable with easily removable crossovers. I gave up when I started to discover SOME of the problems Drew spoke of. These projects are best left to the technically gifted who enjoy the construction as a pleasure in itself.