I really want switchable, individually suspendable workspaces as an OS feature. A workspace for each development project, one for each writing/research task, one for time-wasting browsing, one for gaming, and so on.
For example you can define an Activity for each project, arrange your windows and settings (ie. desktop shortcuts, widgets, etc.), work on you project, then switch to a different activity. When you come back to your project, you'll continue from where you've left.