Short and simple.
Currently the SubUV Animation looks at the alpha channel of a texture, please allow for the option to specify which channel the tool looks at.
With all the optimization I/we are doing, I tend to stick 3 different uv-sprites in the RG and B channel.
This is results in not being able to use this tool properly
And an additional possible addition, perhaps let us control the shape of the sprite sheets it emits.