With new hybrid team forecasting you can:
1) Start with a team forecast with a start date, end date, and a percentage of time the team member will work and have a full team forecast
2) When you create your workplan forecast if it intersects with your team forecast, it will replace it
In this way you can block out team members for a period of time and when you create your workplan the "better" forecasting will replace the generic forecasting for that period.
A new forecasting source has been added called Team/Workplan Forecasting. This combines some aspects of Team Forecasting with some aspects of Workplan Forecasting for a hybridized approach. See Forecasting for more information.