It is possible to implement a wildcard permission check (which allows all actions for a given permission target), by omitting the action constraint for the PermissionCheck in your rule, like so:

rule CanDoAnythingToCustomersIfYouAreAnAdmin
when
  c: PermissionCheck(target == "customer")
  Role(name == "admin")
then
  c.grant();
end;

This rule allows users with the admin role to perform any action for any customer permission check.