Basically I would like to make the layer boundary size content-aware so it will always fit and never limit content to spread.
Example A (Default GIMP Behavior): Here the layer "Layer" has the same boundary size as the canvas no matter if is just one pixel of non-transparent content or the full layer.
Example B: Here the layer "Layer" has the boundary size of its drawn (non-transparent) content. And If I just kept using the brush towards any direction the layer (and consequently the canvas would scale), in red was the layer boundary when I first draw something, and in blue (and the right and bottom red box) would be after a second draw has been made.
This was brought to my attention when I unsuccessfully tried to move a content to snap to a guide rule, however it only snapped to the layer boundary and not to the content.