Allow creating persistent volume onto a separate device
For added plausible deniability I suggest adding the option of being able to install the persistent volume on a separate device other than the one running the OS.
This way Tails OS mass storage device 1 is physically different from Tails User Data mass storage 2. User data may be stored on easily concealable/disposable/hidable MicroSD card ; if properly concealed an oppponent cannot prove nor disprove whether Tails was used with or without persistent user data.
Boot sequence could look for external /home directory then revert to internal temporary /home if none are found.