The most common use for work types is for the type of activity being performed as opposed to the person, but Intervals is pretty flexible with how it handles work types and you can create rates per person. We have seen a lot of different ways to do it. For example:
Junior Copywriting
Senior Copywriting
OR
Bill – Copywriting
Sam – Copywriting
OR
Bill – Rush Fee
Bill – Regular Fee
Bill – Non Billable
When a new project is created the defaults get pulled into the project and then you can delete work types (people) that are not needed for that project and edit the rates if needed for that particular project. If you have a lot of people the drop menus could get pretty big and people will see other people in the drop down menus so that might be a concern. Also, there is not a way to set a default work type for each person so they would have to select their name from the drop down menu.