I can understand why you would be asking this of us if you have not lined up your Luthier yet. You want this to be a special Bass, that you have a lot of direct involvement in. That makes sense. When you find the right Luthier, and by "right" I mean someone who is skilled, and not a knucklehead built 5 guitar hobbiest or wannabe guitar tech that does set ups off and on at your local music store(no offense to highly skilled techs that have building experience). You should discuss your thinking on wood selection, design and so forth with that person. Don't rely on random bits of info you pick up along the way. Use the knowledge and experience they bring to the plate. That is how you will get a fine instrument. They will know what will make a differnce in the overall sound, reliability, and playability of your bass. Much of the info you get will need to be put in perspective as to its actual impact(many things make little or no difference, and some can pose real poor performance). Put your faith in their experience(if you don't trust them find someone else, because you need that trust).
Have fun with it, and good luck with your recording.
Peace,Rich
Cheers, Rich. Of course I am not pinning all my hopes on what is said on some internet forum, but I was hoping to find some ideas and opinions, albeit objectively and constructively given, from as many sources as possible. Obviously I am not going into this build with a hobbyist builder in mind. I have one or two in mind that I have also been in contact with already and they both have a good record of custom builds. I also know that the internet is full of people that like to argue about nonsense just for the sake of it. But then again there are some people out there that are worth sharing ideas with. By the way, Supernova I never asked about the suitability of purpleheart for instrument building I was asking if it would be a dense enough wood for a neck-through construction to use with zebrano. I have played instruments that have purpleheart neck-through constructions but they are usually with ash.
Anyway, that said I have pretty much got what I wanted out of this thread. Thanks everyone, especially Rich.