Infused gems aren't really designed to be used as 1 use items. I mean.. well, they are, and you can use them like that, but they're better used to make a wand which uses 4 infused gems and has 10-20 uses depending on the spell.
Setting a gem of light into a ring would be allright, but there's not going to be a system that allows all infused gems to be set into a ring and become 1/day items. Light would be fine since it has 0 impact in the game. But going from a single use item to a 1/day is huge.
Also, "ring, weapon or armor etc." Even if you only used the spell light, and made a recepie to set a gem of light in every ring, weapon or armor, That would add like... 800 new CNR recepies and items in the palette. I realize I'm taking you far too literally, but I'm just making a point. You can hire someone to cast continual light (or cast it yourself, or use a scroll) or put a damage resist/enchantment on an item that will add light of various colors to it. I'm thinking those options are good enough.
Oh, and you can't use scrolls to fufill a crafting recepie's requirement, I've tried
-TV
