What is the preferred method to auto-start b43, at boot?
I've probably had three different sets of broadcom hardware that worked with the b43 module and firmware obtained using b43-fwcutter (my current hardware will only work with the wl module):
If the wireless-KERNEL extension is loaded at boot, the b43 module will load automatically as long as the wifi hardware switch is in the "on" position.
If your broadcom hardware requires a home-made (using b43-fwcutter) firmware extension in order to work, this extension needs to be loaded before the wireless-KERNEL extension.
So, whilst you're figuring things out, it's better not to load the wireless-KERNEL extension "onboot".
Once things are working, I believe you should be able to load your home-made firmware extension "onboot" and run the wifi script from bootlocal (which will load the wireless-KERNEL extension).