Consider using DwarFS #36

https://github.com/mhx/dwarfs is making bold claims:

So in this comparison, mkdwarfs is more than 6 times faster than mksquashfs, both in terms of CPU time and wall clock time.
In terms of compression ratio, the DwarFS file system is more than 10 times smaller than the SquashFS file system.

It'd be interesting to do some real-world comparisons by recompressing existing AppImages in DwarFS.

Reference:

• https://github.com/Phantop/appdwarf