While Stardew Valley has a pretty nice spelunking system, you can’t really do anything with the ores you go and dig up besides make them into bars. I think that it’d be a really nice addition to the game if the character could go on and turn the farm into a smithy, where the player can actually process the metal from start to finish, be it into weapons, fishing tackle, horseshoes, etc. Something to give the mining aspect some more depth, and give players more opportunity to choose how they eek out an existence in the game.
while I agree with Zosa, maybe just make it unique items? like, instead of making things that could be made by other shops, you could make furniture, or create upgrades of other items!
It wouldn’t make them useless as Clint would still have to upgrade your tools and Willy would still sell fishing gear, and they both would sell things that the player cannot make, as well as Clint already selling the already smelted bars of metal, which could still be bought in bulk to save time or cut out the mining aspect if people just wanted to smith.