Ability to add multiple bookings to a job role in a Workload Chart

During the project planning phase, a Project Manager will create a high level WBS for a project. Job Role A might be involved in Phase 1 and Phase 3 of the project but not Phase 2. We want to leverage the booking functionality to block out their time against the project so what when Project Manager B plans their project, they can see that this resource is already booked to another project and to consider the future capacity of this role. 

It would be great if there was a way to create multiple bookings for a job role to take into consideration that one role is involved in different phases of the project. Currently you can create one booking per job role (and assignee!), per project.