One of the main advantages of using KDE is the amazing amount of customizability one gets from the plasma desktop. I believe this freedom should be added to other parts of the desktop environment. My idea is to make it possible to add plugins to the title bar of applications.
This is, in a way, already there, as it's currently possible to add and remove different buttons. What I propose is to extend on this functionality: make it easy for developers to write simple plugins which can be added to the titlebar, and offer a GHNS interface to add these plugins.
Many of the ideas that are currently floating around here could be implemented in this way:
If all plugins are forced to be simple buttons:
http://forum.kde.org/brainstorm.php#idea64847 (a button which resizes the screen tot maximum size without overlapping other windows)
http://forum.kde.org/brainstorm.php#idea82868 (Title bar per-application volume buttons)
If plugins can be anything (not just buttons):
http://forum.kde.org/brainstorm.php#idea61999 (Combining title and main menu bars)
Can't seem to find the url (group multiple windows of the same application (google chrome style))
The advantage of this system would be that these plugins would be very easy to add for users, but they wouldn't get in the way of users who don't want them. It would also allow extreme amounts of innovations as everyone who has an idea would be able to implement it by themselves, and it doesn't have any disadvantages as nothing changes for users who don't care about these features.