Yeah Brigade Quartermasters used to sell a Brit style Gortex suit that was designed to be worn under the parka or windproof smock. Arktis still sells something similar (and probably made the BQ suit) since guys over there do this all the time. I use a Red Ledge "Thunder Light" jacket and trou, which is a very light, one-layer WP system, not much thicker than a windshirt and trou, which works nicely under the smock and combat trousers. They have been extensively tested on combat deployments by SF dudes, which is where I found out about them. Very light and packable as opposed to issue gtx stuff. They are very reasonably priced, especially when compared to Gucci stuff that costs hundreds of dollars.
This smock is already spoken for. Will be sending it out to a buddy this week for his testing.
Yeah I just like the concept of having a single outer layer, which is camo'd for visual and NIR, doesn't glint in rain, or make noise when busting bush. I'm not surprised this concept is being re-visited.