After a day of -12C riding last week it was obvious shoe covers and heavier socks wasn't going to cut it. At the very least I would have needed to go to a larger shoe to make room for thicker socks, but my then my shoes covers probably wouldn't fit.
I briefly considered clipless sandals, with felt Sorel liners and some sort of wind / water proof cover for the boot liners. It probably would have required a very large sized sandal.
In the end I decided to bite the bullet and order a pair of Lake MXZ302's. Not having to mess around with shoe covers before riding will be nice.