For projects that use a grid (tileset, animation, etc.), having a way to move the image contents into a grid after changing the size of the image would save a lot of time, especially if it does so across layers.
Choose the width and height of cells
Choose number of rows and columns
Have an option to clear existing guides and add new ones along grid lines (using the same function that the Add Guides dialog calls)
For projects that use a grid (tileset, animation, etc.), having a way to move the image contents into a grid after changing the size of the image would save a lot of time, especially if it does so across layers.