A modern TTabSet like component for Firemonkey which would allow the creation and manipulation of Tabs. Tabs should be pinnable, moveable and closable. Also Additional tab buttons like a New Tab button adjacent to the last tab.
The VCL TTabSet is very old both in features and appearance. The Firemonkey TTabControl is also very basic, A new modern cross platform Tab control would be great.
In my opinion the Tabs for Google Chrome are the best around and a component with a similar feature set would be fantastic.