No, "completely shot" would be constantly struggling with a rapidly shifting bubble of air in the drysuit and/or suffering an injury from an uncontrolled inverted ascent. Too bad....
As was mentioned, there are lots of ways to improve heat retention if you've got to dive wet. I'm a big fan of strategies for retaining body heat before and after the dives. That can make a HUGE difference in comfort during the dive whether you're diving wet OR dry.
The grossly oversized drysuit isn't really a viable option, nor would it be fun.... Instead, I'd plan on diving wet, then eat well, wear winter overgarments to stay warm when gearing up and I'd pour plenty of hot water into the wetsuit when needed.
It's easy to bring ten gallons of hot water in an insulated container. A plastic garbage bag can keep the water from spilling, if needed. Blankets can further insulate the container. That hot water will feel real good later!
Good luck and remember to enjoy the diving....
Dave C
