Exuberance has long been the Missoni MO. Pre-fall isn’t as up-all-night-dancing-wild as Angela Missoni’s Spring collection was, but when the weather turns especially frosty next year, fans of the brand will be happy she didn’t rein in her penchant for layers. With its focus on outerwear, the house’s latest outing is particularly cozy.   The waist was a focal point. Margherita, who’s responsible for the house’s accessories, is a big believer in belts, the wider the better.  Among the highlights: a long poncho in a purple and gray space-dye knit and a sleeveless vest with beaver and fox chevroned fur trim, as well as the oversize coats in a furry knit that the family is calling pelliccia.    Underneath all the outerwear were dresses with a more body-conscious fit than we’ve seen in a while chez Missoni; the form-fitting silhouettes for the most part came courtesy of a puckered stretch leather.   The real news here, though, was the eveningwear. We don’t often see true formal dresses at Missoni, but there was a stunner on the racks in the form of a sleeveless sunflower yellow column in a macro floral print with a densely sequined bodice.