So as a Magic Mod that seems to be gear centered. Admittedly I've never gone far in this mod but I have a few ideas here.

1. Spatial Pockets Thread: could be a thread that when added to the armors adds a Backpack similar to Sophisticated Backpacks different tier thread having different size storages or other ways to upgrade.

2. Portable Hole Spell: similar to an ender chest creates a linked storage that looks like a hole in space? could be linked to storage lectern?

3. Bags of Holding: Going back to dungeons and dragons here, could just be literally backpacks also similar to sop. backpacks. Just a craftable bag from Magebloom.

Anyway just some ideas