Something that can be especially useful in larger servers with complex organizations is the ability to create "subroles--" or the ability to make certain roles inferior or superior to others without affecting the role hierarchy of the rest of the server.
Let's say that I run a business and use Discord to communicate with my employees. If I wanted to give the manager of the sales department the ability to manage roles in the sales department, I would also be giving them the ability to manage all of the roles beneath their own that might lie outside their area of responsibility, when I may only want to give them access to one or two. With subroles, I could make the roles in the sales department inferior to the sales manager role. That way, there is a clear hierarchy between those people, and the sales manager wouldn't have the ability to mess with other departments.
In the above diagram, the sales manager would have the ability to manage the sales and marketing roles, but he would not be able to manage the production, logistics, or finance roles, even though he is above each of those in the role list.
One objection that people may have to this idea is to just give each of the managers a "manager" role rather than give them specific "sales manager," "production manager," and "finance manager" roles. The issue that arises with this is that then those three people--since they have the same role--would be able to manage the entire company rather than just their department. In some businesses and communities, this is not desired.
As Discord continues to grow and is marketed towards a wider range of people, it should be able to provide for the needs of businesses and other organizations with complex organizations. The introduction of subroles would allow businesses to create a communication platform that works for them, and it may influence some to make the switch toward Discord. Discord took a step in the right decision when they added the feature to allow roles access to manage only certain channels and channel categories, but if they want to take another step in the right direction, they should implement subroles.