The only way I want spell making back is if existing spells are an actual, viable option. They weren't in OB.
Anything you could create was automatically better than anything you could get elsewhere. It's not just a balance thing, but something that makes sense - NPCs are around to put months, even years of work into magic and the PC can whip something up in ten seconds that will beat anything you'll find anywhere. So add things to the world that make default spells a viable alternative - hidden or ancient lore, quest rewards, etc. Even with unique effects.
Think Finger of the Mountain, but in this case not inferior to the PC's own cooked up Shock spell.
The problem i have with this argument is that you make it sound like adding SC would automatically make every destruction spell in the game useless.
Alvor has put years of his life in becoming the best blacksmith he can be, and all i have to do is make a fine steel sword at lvl 1 and i already have something better than he has ever made.
And i think SC Could be done with it's own skill. Maybe the first perk could reduce the cost of all spells crafted by ~20% like the other crafting spells, so NPC sold spells would be superior at first, and if you want them they're there, adding SC isn't gonna change them from what they are now. But, if i'm dead set on being a purely DOT mage, i could put my first few perks into the SC tree and try to become more efficient with their use.
I would really like SC to be like alchemy a little, where store bought spells are superior to crafted ones at first, but crafted spells eventually become stronger if you put the time and effort into it.
I don't mean to sound condescending if i do.
Thing is with limitations this would literally become the "bigger fireball" style of spellmaking where you don't really make spells, instead you just tweak already existing ones. This might fix the "destruction is useless after level 40" problem, but so would scaling spell effectiveness with skill and that wouldn't cause that many problems.
isn't that exactly what enchanting is? you don't make your own enchantments, you tweak existing ones. why si that fine but not sc?