Personal warmth is really just that, a personal thing. But for me, being a Tasmanian, not a Queenslander, my torso is the area I get cold if I am going to get cold. My legs are not usually an issue. Yes my extremities are protected, EG, Beanie, gloves, warm dry socks etc but just a set of thermal pants of some sort as someone else suggested is more than enough for me. If it is really cold I retreat to me sleeping system.
Having said that, I have been absolutely freezing using my supposed cold weather 'system', not realising that I am still wearing dampish base layers due to sweating, and when the temp dropped I froze. And yes, I should have been experienced enough to know better.
A dry set of base layers along with your usually cold weather clothing for when you stop will see you through december on the OLT IMHO