In our company we work on Two types of projects. Ideally we would have two project backlogs and one scrum team for each. However, only half of our company specializes in one of the types. The remaining half works on a combination of the two types, depending on priority and backlog. What is the best way to set up a system where we have two scrum teams with simultaneous sprints pulling from one backlog AND to occasionally have people on both teams working on tasks within the same project?