Different user roles in different projects

We have people with different roles in different projects.
Eg. X is a project leader in project A but he is developer in project B.
For this scenario I set up groups for each project like this:
ProjectA_leaders
ProjectB_leaders
ProjectA_developers
ProjectB_developers

etc.

I assign people for the group corresponding the role in their project.
The big drawback with this workaround is that I'm not able check group permission (roles) in workflows only if I create separete worklfow for each project.

An idea to solve it to have project roles schemes. This would allow me to assign peoples for groups in a scheme and assign this scheme to a project.

Or is there better workaround than what I use?