User blog comment:DeathGodPrayer/Talk About What You Want!/@comment-6482575-20140113044029/@comment-16281343-20140113045312

One volume solely dedicated to the Vali team may be to grand.

Maybe a Volume comprised stories of how the teams other than Rias' was formed.
 * Sitri
 * Bael
 * Vali

The setting could be like what happened in Volume 15, where they are just casually reminiscing or telling stories. A nice setting could be.. when the teams are taking a break from training under Sun Wukong, they told stories about their teams.