Thanks for your useful answers and interesting input.
I've been also wondering about using an internal gear hub (Rohloff in my case) driven by a chain encased in a chain glider, but I'm not sure about the friction between the chain and the case itself, and noise generated by it.

If I could ask you a few more questions.

What is the bike frame made of?
What type of brakes is used and how would you assess their work under the conditions in question?
Do you use dynamo-powered lights? If so what dynamo is it? Have you come across any trouble using the whole system in winter? If you run/know of a lighting system based on different source of power which you find better-suited for winter conditions, please let me know too.