The Spreadsheet widget is a good start, here are some additional ideas:
1) Ability to assign specific data columns to a spreadsheet column in DataSource data binding and format them.
2) Control tools that can be visible in the toolbar as well as add custom toolbar items/tabs
3) Enabled/Disable or Show/Hide tabs in tool bar. Alternatively, be able to add custom tabs and toolbar items as well.
4) Events! need more events. Cell selected, Range selected, column selected, etc...
5) Disable/Enable certain commands (such as Cut, Copy, Paste, Delete) based on #4 or other criteria. Useful if I do not want specific cell or column data copied or deleted.