This makes me think you haven't had much touring experience - at least not lately. The rest of this is predicated on that, so if I'm wrong, please ignore.

The ideal touring setup is a very individualized thing. What I would consider near-perfect may have many flaws from someone else's viewpoint. My suggestion would be to buy an off-the-rack touring bike (there are lots of excellent choices) and tour for awhile. While on tour, write down pros and cons of what you have, and start to make a list of what you would want on the ideal bike. When you have a pretty clear idea, then consider dropping the bucks for a custom rig. You can always sell the first bike for a good price - good touring bikes hold their value well. It might be harder to sell a custom than an off-the-rack, if the custom involves choices which aren't mainstream.