I am currently working on a multi-tenant applications with many features, as the systems grows, tweaking and refactoring this system becomes more difficult and cumbersome.

The problem: Due to different client and users requirement, I have to add new feature and most of the new features is not relevant to other groups currently in the system. Currently I am trying as much as possible to allow turn on and off of each feature for different group of users so only the enable feature shows up on their dashboard.

Stacks: NodeJS & PHP, AngularJS and MongoDB, Express

Question 1: In what possible way can turning on and off features possible without breaking come part of the system ?

Question 2: How is building an application with the wordpress kind of architecture possible, were I have to develop base script and create APIs and hooks to communicate with the parent code base ?

Links to tutorials and sample are welcome