New parameter for margin setters to counteract movements of components in composites?

[madig]

I noticed that in Glyphs.app, when you manually change the sidebearings of a glyph, the app will counteract margin changes in composites that use that glyph as a component. It doesn't do it under all circumstances (e.g. using HT Letterspacer won't trigger the mechanism, at least all the time(?)), but I wonder if ufoLib2's margin setters should get a parameter to do the same?