Basically an interface that lets you select multiple styles and add-ons for removal, and an interface that would allow you to select multiple styles and add-ons to be disabled/enabled.
I'm a huge fan of this, the waiting for rebuild takes longer than the clicking, so doing all the clicking and walking away would be a nice thing to have.
We can surely use better addon and style management. A lot of webmasters are using/installing a significant number of addons & styles. Rebuilding again and again doesn't make much sense and can add up to a lot of time.