Well, I was not talking about fonts, no.
Most of my atlases have over 30% wastage.
I am sure I can organize them better, but I always like to keep the atlases logically organized as well, so I am not mixing elements in one atlas just because I have space available.
I am never using mipmapping, as it is my understanding that for 2D, pixel perfect, I dont need any.
If indeed a smaller PNG means it takes less space in the final build, then I suspect most of my atlas.png files will enjoy 20-30% reduction in size, which is quite a lot.
Of course, if I am wrong in my assumptions, or the addition of such feature will bloat the plugin, then lets skip it, but if I am right, I would love to enjoy this reduced size.