Ugh, having sailed our T in 0-5 degrees Celcius in a wetsuit+windblocker, and had the first degree frostbite to prove it, I would choose any non-breathing drysuit over a wetsuit in the cold. A breathable drysuit would be even better..

Fleece lined booties?? That sounds really cold if they become wet. Wool is what keeps you warm, even if wet.

You are right on with regards to keeping your head warm. The head/neck constitutes 90% of the bodys temperature loss to the air (elementary norwegian army winter training course teaches this, the winter survival course teaches you the rest you need to know). Wearing a woolen 'head-over', or loose neck with your alpine cap takes care of your head.

All this depends on just _how_ cold it is when you go sailing, of course
We tend to put the boat in storage when the sheets freeze..