IIRC, ebony is actually a fairly "dead" wood compared to most....
Density doesn't necessarily translate to sustain, and realistically why iterate wood choice so much when sustain is purely an acoustic phenomenon? I can't see anyone holding a LP up in the air and telling you it'll sustain for weeks. Or you'd hear it if it was being played.
Maple is a better choice for sure, but sustain is a pointless goal when a compressor and/or a little feedback achieves that aim much better than an instrument will.
Unless you want to hold a note for a day out of pure aesthetic minimalism :-D
Just me being silly here. One-piece would make for infinite bragging rights, as mentioned previously, but would be a huge case of diminished returns on the acoustic properties.