I live in this 34FK full time, and have for 3 years. Like most of the other respondants, I will agree you won't have a chance.
The walls in a Work and Play are 3/4" plywood with a gel coat on the outside and a thin layer of fibreglass material on the inside, then the paneling. Total R value is R-1. The ceiling has 4" of fibreglass batts, good for maybe R-6. The walls will form ice if the temp outside is below 25 deg. No real chance of keeping the plumbing from freezing no matter how many mods you make. Plain and simple these are a 3 season trailer.
I was in Witchita until mid December one year, and it was not pleasant. I stay in areas(Gulf Shores Al or Houston area in the winter, any farther north just wouldn't cut it.