When you cast an ability say like Cloak of Thorns on another it automatically casts the level the target can use based on their level. Could that same be done with spells? Have each spell cast its level or lower, IE: a T3 could cast a 3/2/1, a T5 could cast 5/4/3/2/1 depending on targets level.
This would allow you to reduce spells in your book and not need hotkeys for differant Tiered spells.