So I was thinking about crafting systems earlier and what I don't like about them - specifically, the grinding and the spammy, impersonal nature of it. In most of these systems, you will make hundreds or thousands, sometimes more, of just a few items, and you can sometimes make dozens in a single sitting. Most of the time any alterations you CAN make are either not actually associated with the smithing or rather superficial, and rarely is any individual item significant.
I'd much rather have a system where each and every item you make is significant and somewhat unique, even your very first iron dagger or whatever. (actually, I'd rather have every piece of loot and every enemy be significant too, but hey you can't have everything so let's focus on crafting today.)
In real life, no handmade item is exactly the same, yet in many games your character might as well be a modern factory making items out of replaceable parts. There's absolutely no personality or character, either to your works as a whole or each individual piece. This seems odd, given what I see as the inspiration for such mechanics - named weapons in many epic fantasy stories, such as the archetypal Excalibur, and often forging scenes for such weapons.
I've never liked how variety and progression is accomplished through material tiers in many games, either. If you don't have variety in each tier, any customization is pretty much totally lost. There's a big difference between chainmail and scale mail and plate, and most of the time these are completely ignored in favor of just having 'armor', despite there being a world of difference between, say, a chain shirt and full plate mail. I'm okay with some tiering, but making cosmetic changes tied to material is just ridiculous, as long as they're the same basic type (like leather or metal)
Fixing this on a cosmetic level would be a huge step for roleplaying immersion, in my opinion, and wouldn't be too difficult. Just make a simple design-your-own sword system that lets you pick a blade, crossguard, and hilt, name it, and boom. For armor just having more styles available than 'armor' would go a long way too. It doesn't need to be too extensive, but not having every player look literally exactly the same when wearing crafted gear would be nice - especially in single player games where identifying another player's equipment is irrelevant.
Obviously mechanically is a lot more difficult. I had the thought of having a minigame where you actually make the item could be cool, along with balancing the economy and available materials in such a way that a single weapon is significant instead of just trash - it takes longer to make and the materials are more difficult to come by but the end result is a bigger deal as well. One thing you could do is have each of the choices mentioned above give certain stats, although making that significant and interesting would require a certain complexity of combat system most games just don't have. Armor can either have mobility scores that make taking certain actions slower, differing amounts of armor on different areas, or just simply different effectiveness against different types of armors (most games that seriously focus on melee combat already do the second two).
There's a lot of things you could do with smithing and other crafting systems that we don't even try to do. I know it's complicated, but surely we can do something more interesting than making 50 iron daggers and selling them for a pittance?