Hey guys, I got an idea to help with Calibretto "little" problem:
(I don't know about Ajna or Calibretto personalities, so I give a generic suggestion who can be changed to fit this characters personalities).
First then all, them whatever we do to call the guest incarnations is used to call Bretto, Ajna will happily welcome the new huge member, but another incarnation states the fact Bretto is too huge to fit the small places the group wanders. Bretto declines the invitation saying he don't want be a problem to the group. Ajna sadly accept the decline but promises find a solution. In this point, Bretto will not join the party.
Now some Incarnation gets a new quest (in whatever way the quest are granted in the Inner Realm). In this quest we need find an item (magical, mechanic, interdimensional) or some itens (to make a magic, potion, seal) capable tho shrink an unliving item (or, in your case, an unliving giant robot/golem). So we go hunt the iten(s) to make the way to shrink your new friend.
After get the itens and make the whatever shrink chimichanga, we can call/summon Bretto again, give the item/cast the magic/whatever and he becomes a part member. But the shrink is not permanent, and Bretto can became bigger or small at will.
In battle, if the party is in small room, Bretto are summoned in a small version (well... he still can be the largest member, even in the small version). Something in the small version can state he are using the "small magic" (like a rune floating in the chest, glows or other effect). If the party is in a large room, Bretto can be summoned in the giant form (or come in small form and deactivate the magic and became larger). In any way, his power will not crippled (I think Bretto cannot want go fight crippled), but his hitbox can be changed with the size.
