Something about Velka style summons and boosts, Rein as a unison device can link up with others as work as a power manager. The way I see this is that she not only increases their magic strength by can actively concentrate where it's needed. Hazard a guess that Lutecia's bugs being Velka based work on the same principle. They link up with the larger drones and concentrate one aspect of their combat power [speed, harder shields, ect].
MC boosts add to the power of an object by channeling more energy. It's slower to cast because of the ceremonial spell, works on a single unit in exchange of additional layers of power.
Velka adds and focuses the existing energies in an existing system. In essense a mass boost to a group that works immediately, though weakening other aspects is just speculation.
Now the image of Rein as miniboss is cute in a fairy sort of way, imagine the girl sitting on mini-Fred as a dragonrider to boost his Blast Flare
