I think I will have my chroot script look for the config file, and if it doesn't find one, it will look in a very few specific locations for a specifically named chroot image.

I will then make a new package (called something like advanced-chroot-config) that will use Bundyo's port of Zenity to interact with the user in setting up a variety of options, including using a partition instead of an img file, and then write this to a config file that will then be used by the chroot script. The new package will also include Matan's unmount script for shutting down your chroot so you can switch to a new one, and maybe some other chroot-related utilities if we can think of stuff that would be useful.