To detect if an ambient is in a compressed BIF and need to be extracted to \override\ (and/or biffed later) to be used in a mod. It'll be a CTD otherwise....
BMs extract such ambients by default right now, but such actions make many duplicating copies. It's not a big deal if you have 100Gb of free space, but it would be nice to have some tools to minimize a size of the final installation too....
So, you're sayind that it's non-trivial task? But you still can detect if for --biff-get to extract properly. Is it difficult to introduce the same detection for a script?