I would like to see charting capabilities within the tooltips. For example, here is a creative solution for putting a bar chart in a tooltip.
If there were a way to have a new canvas (sheet, dashboard and tooltip) allowing for any kind of chart in a tooltip. It would be possible to have a map and assign a tooltip canvas with a bar chart, line chart, bullet graph, table or even a small set of charts. A bar chart by category (apples, bananas) could have a tooltip with a line chart for sales over time for that category.