What ideas haven't been implemented that you're going to work on?

At the top of my list is taking unstructured workbooks and adding a sheet to tabulate inputs and outputs. A lot of spreadsheet models are not set up for bulk evaluation or retaining old results, and the peculiar arrangement of cells constitutes an ad hoc user interface for the model. I want to take that seriously as a programming environment for subject matter experts and give them an extra tool for working with their models. As programmers, we give spreadsheet authors far too little credit for intelligence and skill, and often blame them for the faults of their platform. This is unproductive, and we can do better.