currently evaluating permissions on a complex object like a map or screen is very hard. permission "helper" could do the following :

display a list of all included elements;
allow to choose user or usergroup (both are important) and show whether this user or usergroup has access to this map or screen;
show access per element (table with status, probably);
allow to filter for accessible or inaccessible objects only;
allow to add access with single operation for a usergroup to the complex object - that would give access to the selected usergroup on all hostgroups that are required to view the complex object.

maybe custom graphs might also benefit from such a feature