I don't like to advertise on the Forum but you ask for a resource and there is a custom builder that is excellent.
Villin Cycle Works, Inc.
3003 NE 19th Dr #3
Gainesville, Fl. 32609
He does awesome work. Was refered to him from Ortlieb, who saw his work at a custom bike builders show. We visited his shop and he took us for pizza and salad at Satchel's. His work is outstanding. We may have my girlfriend's Motebecane Mixte fixed and repainted after an accident she had.
I have a Comotion Norwest Tour, will be 60 this year, I love my bike and I wanted a sport tourer. However, you are looking on the plus side of 4k and close to 5k with S&S couplers. The Pangea is an excelent expedition bike. I would go with the Rohloff drivetrain. Thorn Nomad is also an outstanding expedition bike too. Sold by SJS Cycling in the UK.
Finally, I know 4 people who went to R&E Cyclist in Seattle, Washington. They market a touring bike under the Rodriguez label. They have 18 stock sizes, if you want it customed $200. They build it from scratch. They all "love" their bikes because they fit like a glove. For a shade over 3k you can get a bike with S&S couples and a case to put it in, that is airline legal, if you go with the 26" tires.
5627 University Way Northeast Ask for Smiley
Seattle, WA 98105-2699
Good luck in your search.