Here's the problem: WS spam alone would create multiple Light SCs (with far fewer difficulties than lowering WS damage o accommodate a SC), and since the Tier 3 SCs are supposed to be more powerful, this would still keep "mandatory SCs" out of relevance.

However, you could make it so that Lv1 SCs lower/temporarily remove magic immunity to an element, Lv2 SCs increase Macc and MATK to an element, and Lv3 SCs lower stats.