Combined workstreams and auto generating schedules

Problem: 

The way our org is set up, we need to be able to auto generate schedules while being able to chose which workstream to generate it for. 

Example: Agent A works work stream A for 8 hours . For the last 3 hours of the shift, agent 8 is also on phones. 

When we auto generate the shift, it creates the different segments based on the forecast. We want to say schedule the entire day for a specific workstream and manually overwrite the hours that the agents would be on the combined work stream as auto generating with both  creates results that are not realistic in a real life scenario with constant workstream changes.  

We thought we would be able to accomplish this by scheduling the workstream as a task instead of a shift. Unfortunately if we add another task it overwrites the whole shift 

Therefor we are not able to schedule our team for ticketwork and phones at the some time which has an impact on adherence, forecasting etc