It will work if:
you are a warm sleeper
you are well fed
you are inside a full doublewall tent(non mesh)
On a very warm and large pad (make sure it's wide enough for the huge winter bag).
Wearing SERIOUS parka, pants and down slippers over heavyweight baselayers, including balaclava
all this fit's without compressing the loft of bag or clothing.
I have a very roomy down mummy bag, maybe 15F rated, that I use regularly with a breathable bivy outside at 0F. Wearing mernio top, full powerstretch top, bottom, balaclava and gloves, DAS Parka, Chugatch pants and huge down slippers. However, I sleep cold, you might get away with less.
One way would be simply to stack up your clothes and bag and measure the loft. How does it compare to a 0F bag?
For other options:
bivy + tent
overbag/quilt (can be anything you or a friend have lying around.)