> Overlay the mounted read-only fs with a read-write fs. Then you can install modules as you like and if you want to start fresh, just throw away the read-write fs. That's what I've done in the past.

It would be nice to be able to build a new read-only filesystem in incremental mode: given a compressed filesystem and some new uncompressed data, incorporate the uncompressed data without completely re-doing all the work.