We currently have 6 tiers of Materia and will likely get 7 in Shadowbringers. The number of Materia levels should be reduced.

A better system would be to always have Grade 1-4.

Grade 4 = Grade 7
Grade 3 = Grade 6
Grade 2 = Grade 5
Grade 1 = Grade 4

Eliminate the current Grade 1, 2, and 3. These grades have been near useless since Heavensward.

With the new information that main stat Materia will be removed,13 types of Materia will remain. This change eliminates 39 items from the game.

On top of this, only having four grades of Materia helps over melding chances, which sorely need to be revised.