An Undo modal/dialog could help. Its "Tagged Undo" subsystem/layer/tree/table could use time-stamps and context tags to distinguish undo actions. This way, for example, Text Editor events wouldn't have to be undone just so that 3D-View actions can be undone, even if they took place about the same time. Not all undoable actions show up in the Info area, so for this implementation, 'Alt+z' would display a dialog of user input events, listed by tag (context) columns, with check boxes in each action cell and for each individual context-based event group.