In A Realm Reborn, would there be a chance for an NPC specifcally made to be a melder. The purpose of this NPC is to be able to double meld and more materia to gear.

Why do this? Gil Sink.

Yes, you could double meld an item yourself, but the chances are so low it would make it extremely difficult.

The Npc however, the more gil you give him, the higher the chance of a double meld. Example:

Ever 100k for the 2nd meld will give you 10% chance of a success. So when you give the melder 1 million gill, you have 100% chance of success of a double meld.

Triple meld will cost much higher, essentially 5+ million gil.

Each Meld costs more and more gil. Also the time limit. Once a month he'll work on your gear. This way it cn't be spammed.

Yes it's high, but it could be potentially cheaper than you or someone you know trying to repeatable meld you gear with more materia.