This is sooooooooo awesome.
On name, I like soul-sword.
4 things:
1. I'd bring the 'meld progression forward 1, so that at first you get 1 meld but no essentia.
2. Making it so that a true neutral character couldn't get into this class would both fit the idea and make it a slight bit more balanced.
3. What melds does it have access to?
Edit: The soulborn list seems very good for this.
4. If you took a few bits from the Incarnum blade, I don't think it would over-power this in the least.
Actually, you could just copy/paste the blademeld chakra bind section.
There's an idea for a PrC.