My own home game has magic locked behind physical items: 6 particular types of jewels that spellcasters need to have in a particular combination for a specific spell effect. I really like the idea of having more than one way to use the physical magic item, though. I already had "use a specific combination for certain spells" and "use a specific combination for magic items or constructs" but you took it a couple steps further by tying it into the economy and afterlife. It's a very interesting development that I look forward to seeing.