If you take a thinner/lighter Apex and sandwich it in between two rather breathable layers of fabric, isn't that kind of like Alpha?
I've done some experimenting with this so far. I made a vest with 2.5 oz Apex insulation in the front, sewn between two layers of 1.1 oz uncalendared and no dwr ripstop nylon (very breathable), and wore it while active from temps between about 5* F to 20* F. Really liked it except at around 20 degrees, think it was a little warm for that, at least when the air was still, but it certainly didn't wet out either and being a vest and having the windjacket fully opened helped a lot.
But, not having actually tried Alpha, i can't say for sure how similar the air permeability is. I do know that with my vest, i can very easily both suck and blow air through the two layers of fabric and the insulation total, no problem. That's pretty cool imo.
I'm not sure why Apex isn't used more in garments, and more over why it's not used with these very breathable lining/shell fabrics. Many of us usually or often already carry around a windshirt or jacket, and/or some rain gear, so "windproofing" becomes really redundant.