Sorry for bump. But it's a strange idea.
The player character "forgot" to bring their shots with them, so they had to use their boss cards.
You select a character, and a kind of spell card set, similar to SWR and Hisotensoku.
Reimu:
Balanced Type: Spread non-spells, Homing Spellcards
Homing Type: Streaming Non-spells, Homing Spellcards
Marisa:
Focused Type: Non-spells shot at enemy in a focused manner, Streaming+Scatter Spellcards
Scatter Type: Dense, scattered non-spell, Fast and Dense Scatter Spellcards
Sakuya:
Time-Stopping Type: Nonspells and Spellcards have Time Stopping, with Sakuya moving din the meanwhile.
Bullet Change Type: Nonspells change directions and speeds randomly, Spellcards have changing bullets when it hits all sides of the screen.
All of this, with the PoFV AI. Easy is super-easy AI, Normal is Easy AI, Hard is Normal AI, etc., until EXTRA has Lunatic AI.
Just a thought.