House Rule: Magic as Masterwork (D&D 5e)

Rather than limit the creation of all magic items to spellcasters, this house rule allows characters with the appropriate proficiency and sufficient talent to craft an item from scratch and imbue it with magical or semi-magical properties by virtue of their skill and effort.

To craft a magical item, the player must have a creation formula that describes the construction, as described under Crafting a Magic Item on pg 128 of the DMG. This formula must be designed for construction using the relevant tool proficiency, rather than magical creation. The most basic requirement is that they must have proficiency with the relevant tools as well as a tool kit of that type (herbalists' kit or alchemists' kit for potions, woodcarvers' tools for bows, wooden shields, or staves, smiths' tools for swords or metal armors, leather workers' tools for leather armor, etc). The DM may decide that certain items or locations are required, just as described in those rules for Crafting a Magic Item. Finally, the crafter must meet a minimum proficiency bonus based on the rarity of the item.

Rarity	Required proficiency bonus
Common	+3
Uncommon	+3
Rare	+4
Very Rare	+5
Legendary	+6

The player may then announce they are going to create that item as their downtime action. They use the Crafting a Magic Item downtime action, requiring materials and time just as if they were crafting the item as a spellcaster, with each day of effort contributing 25 gold pieces worth of progress towards the total required. 

Any number of characters may combined their efforts, contribute 25 gp worth of effort per day towards the completion, but each participant must have the required tools, tool proficiency, and proficiency bonus.

Once completed, the item is indistinguishable from one crafted with the use of magic.

As with the Crafting and Crafting a Magic Item downtime actions, a character can maintain a modest lifestyle without having to pay the 1 gp per day or a comfortable lifestyle at half the normal cost.

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This is another house rule that I end up reproducing some version of in virtually every edition of D&D. Because of the way 5e integrated their crafting rules, this is certainly the easiest edition I've ever done it in. It's based on the ideas of the ancient eastern swordsmiths, dwarven smiths, and elven... well, every kind of ancient elven craftsmen. The idea that exceeding skill can produce items of exceeding power is, to put it mildly, not uncommon. Further, this gives extra utility to skills like herbalism, alchemy, and the variety of artisans' tools that don't generally see a large amount of use. The ability for a jeweler to craft magical rings, or a tinker to decide they want to make their own Apparatus of Kwalish makes everyone else at the table suddenly reconsider any boring decisions.

The biggest benefit that I've found from this type of house rule is that it moves the responsibility for ensuring that everyone has the bonus gear of whatever they want off the shoulders of the Artificers, Wizards, and Clerics, who probably want to be researching and crafting the things they're interested in, and onto the shoulders of the characters who want to wield them. This goes a long ways towards smoothing out the disparity of casters wanting downtime while non-casters view downtime as something the casters demand which is time that could be better spent in another dungeon harvesting treasure and blood... by which I mean experience. Meanwhile, there are few greater joys in life for a Fighter than getting to slay orcs for the first time with the magical sword they crafted themselves.

I'm not sure I like the idea of requiring formulas for magical crafting at all. I understand the logic; it places control of party's resources in the hands of the DM. On the other hand, it places total responsibility of the party's resources in the hands of the DM. This means that, either, the DM is going to waive away this requirement when he discovers that one of the players wants to do something very cool, or that he's going to essentially give the party a magic whatever without giving them the actual item. Either way, it seems like an idea that's cool in theory but cheap in practice. I expect that I'll be posting rules for research in the future.