Isaac is working on a FATX library which is more for 360: http://code.google.com/p/x360/wiki/Changelog. But since by design, it caters for endianness and xpart-dm relies on dmsetup, there is some hope that this FUSE driver may bring FATX support eventually to a 2.6 kernel.
Stay tuned. The developer was last working on it in Jan 2011. Coupled with this: http://forums.xbox-scene.com/index.php?showtopic=716721, it's not too far-fetched to combine the two together for proper FATX support in a 2.6 kernel.