I don't think you ever have to apologize for wheel threads in the clyde forum. It's half of what this forum is about. Weight loss being the other half:-)
It sounds like your hypothetical build isn't far off one I've been contemplating lately. Mine has been for an all weather, disc braked, road/cx bike capable of handling at least 28mm tires and full fenders.
I agree that 4X may be unneccassary. The Dyads are both wider and deeper than the Synergy's. Subsequently they may be a stiffer rim and may offset the advantages of the OC drilling of the Synergy rear. You would have to talk to someone who has built with both or Velocity to get a reliable answer. Another rim to consider in that general class would be the HED c2 Belgium. Any of those would be acceptable to me for such a bike. With regard to spokes: front 14/15db, rear 14ss or 13/14sb drive side and 14/15db non drive side would be my preference, brass nipples and I probably would opt for standard stainless unless there was a compelling reason for the black.
Before you get too excited about Prowheelbuilder's willingness to ship to AUS check their shipping charges. When I was trying to get rims sent to NZ, the shipping charges were prohibitive. I ended up using European distributors instead. International shipping out of the US seems to be stupid expensive in most cases.
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