Will SlickStack ever add any type of user interface?

No we will never add any UI or GUI type interface. The reason is because we want SlickStack to be as lightweight and secure as possible. Plus, this approach allows other services to build on top of SlickStack, for example if an agency wants to offer server deployment premium interface they can use SlickStack as the backend. We want to have a truly useful and integration-available approach to LEMP servers for WordPress that various players can reference and build from.