Alright, before I get into this, I do want to say: Yes, I know this, if it ever gets added, will not get added for a long, *looong* time. With that out of the way, it is the simple way of making a weapon, which looks usually just like any other weapon of its make and origin, different. By using already existing items in game, that being, gemstones. Just like dying armour, one can add gemstones to their weapons to add a bit more detail. The most optimal places to add said gems on a crafting bench (regular crafting bench for ALL weapons, as it isn't creating that faction's gear, or modifying its' statistics in any way) are on either side of, say, a sword, which would add the the gems to that specific side of the cross-guard, at the bottom, for the pommel, and the top, for etching the stone into the blade. Occasionally, one can also see captains, and other high-ranking soldiers with said gemstones in their own weapons.
As an optional way of creating a custom weapon, there should be an NPC called a Jeweler, who, as the name suggests, deals in precious stones. He would be the main Merchant to sell and buy the shiny rocks, and, instead of the Smithing button, have the Weapon Inlay button in its menu, which would allow the player to place in their weapon in a single slot surrounded horizontally and vertically by other slots where one puts the gemstones.
Please note: this CANNOT be shapeless crafting, for obvious reasons.
If this could go further, possibly allow armor to also be modified in such a way? For leggings, either side for knee-cap jewels, for chestplate, above for front, below for back, and either side for pauldrons embellished with stones. Same for helmate, top for the front, side for, well, either side, and below for the stone at the back.
And finally... yknow how, with the suggestion's implimentation, dwarven armor has the ability to inlay metals as well as jewels? Maybe their weapons can also soley be able to have metal additiomns, like the back edge of the sword having the silver gleam of Mithril, or the edges of the crossgyard etched with gold.
Apologies for the bad grammar, I had to write this quickly on mobile so my mom could get her phone back, and my thumbs started cramping XD
TY for reading!