Currently in ACR, there is only one set of settings that applies to all three of the adjustment tools: Brush, Radial, and Gradient. If you adjust settings in one tool, then select a different tool, the settings will be the same as what you selected for the previous tool.
This doesn't make sense to me. I use each of these tools for very different purposes. Settings for one adjustment tool are completely different from settings for the other tools. It would make much more sense to have separate settings remembered for each separate tool. Then when I edit several similar images, the settings I used in the previous image for each of the tools will default to what I used for that specific tool on the last image.
This should be a very simple add.