It sounds good and not too bulky, as your mid layers are thin.
I'd rather not buy new gear for the mid layers, if possible. The R1 looks nice, but I think my slim fit elastic fleece would do in this situation. For head protection, I have got a hat that covers the ears and a thin balaclava as well (if needed). Not to mention the hood on the outer shell.
My jacket is not one of the harder, heavier ones, and it's actually comfortable to wear while on the move in snow/wind conditions. It's a 2-layers GTX.
Windshirts: I go back and forth on those -- I can see how they would be useful in warmer weather, but once you go that high, the outer shell seems to be more appealing. I have got a couple of lightweight ones I wear for running (full zip, no hoodies), would one of those suffice? Looking at the Houdini, it seems to be a lightweight, pretty thin nylon jacket.