BUT if a user is using Rembrandt he could discover some ugly side effect, under some conditions the developer can compensate it .
Again - the aircraft should not touch any settings which are configured by the rendering GUI dialogs unless the user specifically requests this. That includes quality settings, filter parameters, the number of passes done for Rembrandt shadows etc. If the user discovers an ugly side effect, the user has to compensate for it (for instance because the developer has no idea of how something looks on a differently calibrated screen and on different hardware).
The aircraft should only set the effect parameters which are not configured by the rendering dialog (such as, for instance, enable normal mapping on if there is a normal map provided - where the user has the option to not use the normal map by selecting low rendering quality).
The whole system is intentionally designed the way it is, I've tried to explain to you a couple of times why (settings being applied to all scenery elements, not only your plane, user confusion with auto-saved settings, multiple systems fighting for control over the rendering settings, configurations which can't run on weaker systems,...) , if you still don't understand why, then please do whatever you feel you need to do in your own hangar, but don't give bad advice in this forum. Thanks.