I'm not sure whether you're looking to buy your first winter tent, replacing your winter tent, or have a three season tent that might do for winter camping except that you need more vestibule space. I'm also not sure where you're going to be doing your winter camping - in Ohio, where I hike, a three-season tent works very well in most winter conditions; however, we don't get two-foot snowfalls where snow loads are a big deal.

However, what I've seen others do if the tent they have works, but they need storage space, is to carry along a small tarp, which the rig as a lean-to or A-frame, then have the tent door open into the tarp. (This works even better with a two-door tent - one door, with its small vestibule, is used for uncluttered entry and exit, and the second door opens into the storage area.

If this won't work in your situation, then I apologize; I really don't have any experience or insight into full-on winter tents.