Adding this feature won't make the C++ styles disappear. It will only make it possible for users who don't know how to make a style plugin in C++ to make their own styles, while other users get to choose between using C++ styles for their performance or using stylesheet styles that may look better to that user. Besides the performance cost, I didn't understand most of the items on that chart, but I think the choice to use this feature should be available for users regardless of the weaknesses QStylesheets may have, because the existence of the feature won't affect any other choices.
On another note: the performance cost of QStylesheets can be dodged by making the Style plugin only parse the stylesheet once, and then return the resulting style to all applications without needing to parse it again.
