apack/aunpack from the atool suite for me [0]. Funny how many solutions exist for this problem. Though I think Unblob is aiming more for binwalk's niche [1].
`unblob` is closer to `binwalk` than it is to `aunpack`
Looks nice! Kind of reminds me of binwalk: https://github.com/ReFirmLabs/binwalk
https://github.com/ReFirmLabs/binwalk might help, it won't generate the visuals but can give you offsets
For anyone else needing to tackle something like this, its definitely worth checking out Binwalk [1]. It is meant for extracting firmware but it works decently well on most files-in-files type data formats.
Yes, I use this one regularly: https://github.com/ReFirmLabs/binwalk
(Binwalk is a fast, easy to use tool for analyzing, reverse engineering, and extracting firmware images)
binwalk is a good tool to use for this, especially early analysis: https://github.com/ReFirmLabs/binwalk