David - thanks for the excellent discussion. Most of this was pretty clear to me, and consistent with my thinking, though I couldn't have explained it as well.
After reading this a couple more times, I still fail to understand the enthusiasm for a bolt-on Alembic. As David said, A set-neck and bolt-on are basically the same construction, so what is it you would hope to achieve with a bolt-on?
I don't think I've seen any detailed pictures of how Alembic builds set necks, but essentially in either case you would have some sort of pocket for the end of the neck, and then make the attachment with either glue or screws. My guess is that it would actually be somewhat more difficult - hence expensive - to construct a bolt-on that was in any way close to Alembic standards.
It seems that essentially what you're asking for is a sloppier neck joint. Without a nice solid glue bond, you'll have more energy loss, and sure, maybe you'll like that particular tone (sometimes...). But you'll also have more problems over time as the woods shrink in different ways, which may possibly change the tone, and I suspect you'll never get quite the same solid feel that you do with a set neck.
Or if I'm wrong about that, then the only other obvious possibility is that they'll do such a great job, it won't sound very much different than a set neck anyway :-) Personally, I'd rather see Alembic stick with what they're great at (and of course, bugging Susan is not exactly a wise move...).
However (Steve), there is another approach you might consider: replacing your bridge block. Take out that half pound hunk of brass and replace it with a light piece of wood. You could pretty easily make one yourself, though you'd probably want to use threaded inserts for the adjusting screws.
Think about this in the context of David's description. You would now have one end of the strings anchored to a different piece of wood, which is in turn bolted on to the body, and of course it will be much less massive. So certain frequencies are going to attenuate sooner (i.e. sustain less), and give you a different sense of attack and overall tone.
I'm about to try this myself, over the course of the next few months - I have several blocks made of different materials sitting on my dining room table.
In my case, I'm not looking for a bolt-on sound, but rather a more woody upright tone, and I think that allowing some frequencies to die out more rapidly will at least be educational, and perhaps even good. We'll see. But this is something that is fairly easy to try, and might get you closer to the punchy sound you want, once you find the right block.
-Bob
