Hi Folks-at-ARMs!

I'm trying to build a custom kernel for an usbarmory (needed for an USB sound card) and got it done with the arm-build-scripts.
There are however some subtle tricks I don't quite understand:

Why is the kernel compiled on the mounted image and not in the debootstrap directory?
Same question to nearly all the other tasks done on the image (kali-myversion-usbarmory.img).
Imho it could do easier to customize the build if all patches/mods would be done to the kali-$architecture directory, and then rsync'd and ubooted to the image. That way the modification and rebuilding process would be a lot faster.
Am I missing something?

Cheers, 5fx