Hi DaFox,
I spoke with one of our developers to double-check on the progress of this, and the long term plan is to move things into plugins where we can, but it’s going to happen slowly over time.
The example that you are giving, OnlineSubsystemOculus, is already a plugin, so you should be able to just disable it in your project through Edit->Plugins.
Also, a note: if you are building the UE4Editor target rather than your game project’s editor, it is meant to build all plugins since it is usable by any content-only project.
Hope that helps!