Suggestion for Hokkaido Winter itinerary

Hi! My wife and I plan to go to Hokkaido from Dec 6 to 11. We are flying in from Singapore to Osaka on Dec 6 early morning, and back to Singapore from Osaka on Dec 12. I know that we are arriving in Hokkaido one week before the ski season and therefore will be missing it, what would be the suggested itinerary in this case? Would it be wise to book hotel accommodation in Sapporo and move around on our own using the Hokkaido Pass? Or is it easier to book local tours in Hokkaido? I am not able to find any land tour packages from the internet, as all that are available are inclusive of international flight which we don't need. Would appreciate any suggestions and advice,. thanks.

I know that we are arriving in Hokkaido one week before the ski season and therefore will be missing it

No. Several ski resorts should be open by December 6.

what would be the suggested itinerary in this case?

I definitely think that you should pick destinations based on your personal interests rather than mine (or my guess of what yours are). City attractions are good at any time of the year. Hot spring attractions, too. But some hiking and other outdoor attractions might not be available in December. Here is a good starting point for your research:
http://www.japan-guide.com/list/e1101.html

I take it that you will be flying from Osaka to Sapporo. Even then you will really only get about 4 free days in the area. Forgive me for saying so but this is neither a time or cost effective plan.