I never thought about the short-lived ref. 86180 you mention being discontinued due to capacity reasons, as you say, with VC needing the movements (cal. 2460) for the Metier D Arts and other pieces. I always thought that the model was discontinued due to lack of popularity.
For me, the 86180 is, or rather was, a very interesting alternative to the 81180: no date, so retaining the pure dial, a sweep seconds hand enlivening the dial in the way that the seconds subdial does this for the Traditionelle Small Seconds, and a very nice automatic movement viewable from the caseback.
In fact, maybe a bespoke Cabinotiers piece is a solution: an 86180 in platinum with the slate gray dial. Perfection!
Thanks for your continued comments.
Best,
respo