That Ritchey is a great option. But where do you get a custom frame for 2400€ (including fork) these days?
I do not know how "custom" the bikes from Co-Motion are, you can specify differences from the stock frame but I do not know about price. And I do not know if you can modify the stock geometry. I have never talked to them but I did consider buying a frame and fork from them about a decade ago.
I was on a group tour a bit over a decade ago, one person had this model bike:
https://co-motion.com/products/americano
His had tandem wheels (no dish on the rear), rear dropout spacing was 145mm, S&S couplers.