The great news is unionfs will be enabled by default, like in FreeSBIE-1.x.
The only caveat is: will it be stable enough? I know Hiroki SATO committed some fixes to it to HEAD just after the “approval lock” on HEAD was removed, and it may be a good idea to backport them to RELENG_7, so that users gain a better FreeSBIE experience. Time will tell.
Matteo’s original post here