As seen in the GIF above, the proposed broom tool would push pixels in the direction of the cursor’s circle while holding down left-click. Using the broom tool while already on top pixels would drag them along. Holding right-click would only drag/push pixels that are the foreground color.
I doubt this is a niche thing, but a tool like this would accomplish something that I could only do with multiple keyboard shortcuts and a lot of effort. Aseprite has had many updates that have reduced the time and effort of doing pixel art. A tool like this seems as if it would help further that goal.
Also, conceptually, this makes a lot more sense than a smudge or smear tool in terms of pixel art. This Idea would even function faster than selecting and dragging occasionally.