Speaking of things needing rationalization: Smelting iron, which the dwarves are supposedly past masters of, requires furnaces which routinely exceed 1,500 °C. Vs. even exceptionally hot lavas are considerably colder. So why bother forming a Fellowship of the Ring, or embarking on a long & dangerous journey to Mt. Doom, when it'd be vastly quicker & easier to smelt local?

Mount Doom is magical/mythic in nature, the birthplace of the One Ring, while the Dwarven forges aren't.

Quoting Elrond during the Council at Rivendell:

> “It has been said that Dragon-fire might melt and consume the Rings of Power, but there is not now any dragon left on earth in which the old fire is hot enough; nor was there ever any fire, save the fire of Orodruin, that could melt the One Ring.”

Also, the Dwarves that took the One Ring for melting would have likely fallen under its influence, postponing the destruction and ultimately keeping the ring as a keepsake, tool or weapon, like most living creatures would... except for some brave Hobbits, which took a longer time to be corrupted.

More fundamentally, this is not the kind of mindset with which Tolkien wanted us to read LotR. It can be done for fun, but if done seriously, it'd be missing the point.