You dont need to use ubifs with ubiboot-02, people really should not be using ubiboot-01 anyways.

Usually on stock kernel you just export AEGIS_FIXED_ORIGIN=com.nokia.maemo dpkg -i opensh*.deb

After that you can just use opensh command and do all the mounting with that.

And as SIP works for other people in openmode, then its most likely that your SIP provider is somehow wierd, or you just have screwed the aegis accounts store to be in secure vs openmode conflict (as that manifests in exactly the symptoms that you describe (ie credentials not lasting the reboot)).