TL;DR
Mods might wish to opt out of supporting certain feature flags, this would give them a method to do so.What ?
It would be nice to be able to mark a mod as incompatible with a feature flag, automatically making it incompatible with mods that activate that feature flag. As an example a complicated overhaul mod might not wish to perform the balance work needed to support the quality feature, currently the only tool the mod developer has to prevent this is marking mods incompatible on a one by one basis.While there are a limited number of feature flags currently, they represent a concice way of grouping features introduced to the engine and used by mods. I could envisage a future where more are introduced and with each introduced the complexity of their interactions with each other increases.
I believe it is currently possible to check during the control stage if a quality prototype other than "normal" exists, so it should be possible for mods to inform users of the incompatability without this new feature for the quality feature flag. I am unsure if current methods for safely checking the enablement of other feature flags exist when you desire to prevent their use. As such native support for this might be the only way to allow such checks.