Warehouse -- storage space should not be an issue.
A nice thick camping pad is a good start. Is your sleeping bag liner cotton, fleece or something else. Fleece bag liners are very comfy when it's cold. Since you're inside and rain is not an issue, goose down is in play; why use an AMK bivy inside? For that matter, a fleece bag liner and wool blankets (mentioned earlier in this thread) would be great -- pillow too.
BTW, a camp stove is a great way to boil water for tea when the power is out. Tea, coffee, soup -- all super easy to make with a camp stove that can only boil water -- simmering is not required. Get a stove and a good supply of stuff that mixes well with hot water. $.02
Thanks Russ. Great point on the space issue. I should be able to carve out a corner in the warehouse. A more robust mattress and pillow are great ideas. I've got an esbit stove but may switch over the a sterno. There may be more heat value there?
The sleeping back liner is fleece and my thinking re: the bivy was that it's easy to to stay warm inside it rather than just in one of the offices.