User-Group-Project

I am worried about the user management scheme. say i have 3 projects, 9 users, and three roles (pm,developer,user). and for each role and project i have one person assigned. Meaning Project A has one developer, one pm, and one user. And Project B has a different developer, pm, and user. This means i have to create 9 groups to effectively isolate and manage permissions. If the number of projects i create grows to 10, i now have 30 groups, 20users. 20 projs, 60 groups, 60users. This is growing quickly.

What if for each project i created series of roles ( developer, pm, user). These roles could be shared across projects. And for each project, i assigned users to a role. and with those roles i controlled permissions for the individual projects.

Now, continuing my example from above, in the case of 20 projects i have 3 roles, 60 users.

Iam interested in your opion on this.