So again, "A" way of doing it. It isn't as ally as a Jay Jay's, Arktis, or SASS, but it works pretty damn good.
I really like the windproof smock concept, as a light, single outer layer which can be tailored to conditions by adding subtracting layers underneath it as required. This gives you much more versatility as compared to multiple layer jackets, with sewn-in insulation and WP layers. Also as a tactical consideration, the smock provides better camo, especially when wet, as opposed to hard shells. It is quieter with less sheen, especially under NIR. So for things like close target recce it is a preferred garment.
To waterproof it, you simply add a single layer WP shell underneath it, like the Thunder Ledge or Arktis jacket (and trou). For insulation, wind shirt, gridded fleece on the move, or puffy suit when stationary. By using a single outer layer, only the smock needs to be camo'd, thereby cutting down on so many expensive camo layers. Single earth-tone colors can be used for all other layers.
The Brits (and others) have been doing this for years, instead of insisting on each layer being camo'd and/or worn on the outside. It just makes sense to me as well.