I like the Ultegra idea. Nitto Seatpost to match the bars and stem. Fenders and 32s (why not 42s) are for your next custom when you decide to go disks. See if the matching Ultegra dual pivots will work with 28s and fenders since your builder can set it up with the pads near the bottom of the slots. Ultegra hubs 32, 3X, DT Comps. How about Crankset? I'd go T.A. Or Sugino Mighty with P.W. BB.
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I don't do: disks, tubeless, e-shifting, or bead head nymphs. But I do hate all e-bikes.