Having additional software such as Owncloud as part of MIAB is nice, but it is not core functionality. Even though for some (perhaps most) users, Owncloud is a valuable addition, it is not part of core functionality, a bug-riddled package with a code base of questionable quality, and it therefore opens op your box to a huge attack vector. I always remove it after install/updates, but the right way is to be able to not to have it installed in the first place.
What about asking in the installation procedure whether the user actually want to install non core functionality components (like Owncloud or webmail)? If there is a desire to keep the number of installation prompts minimal, what about having install flags (e.g. --exclude-owncloud / --exclude-roundcube ) that allow you to exclude non-core components from the installation?
Cheers,
JeGe