Selection brush tool needs dynamic opacity

PHOTOSHOP DEVS: The Selection Brush tool is a great way to take a rough idea and generate derivative art by setting the opacity around 50%. The only problem is I will usually need to adjust the opacity up and down to get the generations that I like (this process either gives the AI more creative freedom or tells it to be more derivative). To do this I need to re-brush my selection each time. It would be great if there was a checkbox called "Dynamic Opacity".  After I brush my selection I just can adjust the percentage in the input field and it will update the selection's opacity, allowing me to run another generation quickly.