Then maybe look no further...
If it is the 321/861/1861 dial layout that you like, then be aware that Omega already sold a range of watches in exact the same form factor as the Speedmaster Pro, with exactly the same dial layout using the 33X3 auto chrono movement (as Al alluded to above). These were the Broad Arrow Speedmasters. These are chronometer rated and in the case of the 3313 used a coaxial escapement with column wheel operation. Omega actually rather perversely also used a manual wind version of this movement in an enamel dialled special. The 33X3 got off to a bad start but by the 3313C they finally had something special, by which time the market moved on. Never underestimate Omega's desire to innovate, whatever you can think of, they have probably already tried it.
There are several dial variants in 42mm and 44mm but here is one I happen to own, the 3313C coax auto movement 1957 Speedmaster, case number 178.0022 (showing how closely related it is the to the 145.0022 Pro). It is a truly lovely piece and criminally underestimated by the market. It is IMHO way nicer with much purer breeding than the so called Grail Speedmaster from the 80s which some misguided types rave about. It is exactly the same depth as a sapphire sandwich Pro, and therefore about 3-5mm thinner than the later in house 9300 auto models, which to my mind were a step backwards.
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