DM-Steg

There is a simple answer to random data problem: just have distributions write random data to every unused sector on the disk in the background after install. Maybe have it as a opt-out checkbox.

I am pleased to see dm-steg and the like for a similar reason. If you've gone to the trouble of installing specialised software (eg, TrueCrypt) then plausible deniability is pretty hard. But now just about every linux default install comes with the tools that can do the job so that particular issue has gone away.