I need to create and maintain a user documentation for a system of which there are different instances in use by different target groups. There are several levels of integration with other systems, several development stages, several regional production deployments. Not all of these instances have the same feature set (e.g. some features are just for tests, some features might be regionally limited et cetera).
Additionally the system consists of single services that may or may not be deployed together which affects the feature characteristic of the overall system as well.
Finding a system that helps any user with one documentation with feasible effort. Currently the approach is to always document the latest development iteration in a versioned wiki system and indicate functionalities that are "just" testing functionalities. Is there a better way to document such fluid systems?