Some modules or features, such as java.debug and timers, are mainly intended for NB developers and QE to explore the IDE's features. (Some like apisupport.projectinspector fall into this category but are currently on AU.) Currently these are either removed from their cluster config in release branches, which is awkward since you need to keep track of them all; or conditionally enable certain features based on whether assertions are on or off, which overloads -ea to affect UI, and make use of lazy registration annotations impossible.
1. Move these modules to Stable AU and let anyone who wants to use them download them that way. Simplest and clearest, though might be annoying if most dev build users want these things on.
2. Make them deps of some kit module in the nb cluster, all disabled by default; you could then enable them in Plugin Manager. Straightforward but means that this kit module must depend on some domain-specific modules like java.debug.
3. Make them eager modules requiring some token which is provided by a module which is disabled or missing by default. Solves the dependency problem of #3.