When I use Spot Healing Brush, and it doesn't do the job well, I want to quickly switch to other tool - Healing Brush (the one with a possibility to select source wit an ALT key).
In such a situation, I always press the ALT key, which is associated with selecting the source for the Healing Brush, but it doesn't work because I have the Spot Healing Brush tool active.
Maybe Photoshop can be smart enough to know that when I use Spot Healing Brush and I press the ALT key, it means that I want to select a source for my Healing Brush.
Then I would not have to switch between tools and two options will be agregated in one tool.