I think this plugin is the greatest WordPress plugin ever. It meets so many needs on company management. After using it for some time, I have some ideas to improve it. I think all the ideas focus on simplicity and functionality.
1. Change the group into taxonomy type and taxonomy can be assigned as group type.
Group is the core concept of the plugin. But I think using taxonomy as group is better.
a. Group management can be replaced by internal taxonomy management.
b. Group table can be deleted.
c. Group can be hierachical.
d. Group can be multi dimentional, not just singl dimention. For example, I need three group dimentions, including organization group dimention, level group dimention and project group dimention.
e. Selecting groups is as easy as selecting categories, and no code is needed, all the work is done by WordPress category code.
f. Exporting and importing groups and member-group relations can be easy because there are some plugins with such feature.
2. Provide AND relation besides OR relation.
When I assign 2 groups into 1 category, it means people in any group of the two groups have the permission to view the post. It means the permission definition is in OR relation. But sometimes I need AND relation. I need people in A organization and B level and C project have the permission. I think it always happens.
OR relation can be done by using category function, the plugin has done it perfectly. When I need both A group and B group have the permission, I can assign A category to A group, B category to B group, and select both A and B categories, then both A and B groups can view the post.
I think on groups layer, permission should be AND relation, on categories layer, permission should be OR relation.
3. If you think the backward compatibility is important, I recommend you develop a new version of the plugin for some pro users.
Please think about my recommendations. I am looking forward to your improvement.