Thanks for all the replies!
I would like to try and address a few of the good questions brought up so far.
Yes, the idea has been tested, but not by us yet. Several companies have tested similar technology, and the insulation benefits with air has some great data behind it. NuDown claims a temperature improvement of up to 40 degrees (f) in their new line of inflatables and We'dz claims similar.
This hood would be designed similarly to what is currently on the market in terms of helmet compatibility. i.e. it will be roomy enough to fit over a helmet, but will have a draw string to cinch it down when not wearing a helmet. The gaps in the hood will be large enough to allow the hood to breath, and be comfortably cinched down with the draw string.
The hood is designed to hold air indefinitely. So there will be no need for continually breathing into the system. breathability is absolutely an issue with air tight fabrics, but being a typical hoodie that is inflatable, the idea is that you can just deflate it if you get hot, and put it down when you get sweaty.
As far as the water sac, we believe this wont be an issue, as it will be similar to an inflatable sleeping pad. There will be some moisture, but not enough to build up, and it should evaporate quickly, and not become a freezing issue. This is something we are testing with the valve currently.
The main reason we focused on a breathable valve, is weight; we do not want to add undue weight to the jacket, which an air pump would add. NuDown has a pump, and the weight is a major downside, (as well as breathability). One of the main benefits of this product besides superior warmth, would be cutting down on the amount of "stuff" one needs to pack. scarves, balaclavas, gaiters, etc...
The jacket is being designed so that their will be a gap in the liner in front of the mouth where the zipper is, and two discrete exhaust ports so that breath will not go immediately up, but rather down and out of the face piece. This provides two benefits; you maintain wind protection for your nose and mouth, and it will limit the fogging on your goggles.
Also I should mention the hood, and neck portions will be able to be inflated separately.
I apologize for not having a better image, but there will be one soon. I'm working with our 3D modeler to get a better mock up to show more detail.
As for the "gimmickey" aspect, sometimes it's hard to tell if a new innovation is simply a gimmick or a really good idea. That's why I would like to get as much knowledgeable opinion as possible before moving too far forward.
You guys are awesome, please keep the feedback coming!