Hello the idea is great. But sometimes you need some other rotation for the skeleton, like if you do 2D for isometric games or top-down.
So it would be great to have also rotation in the other axes.
Another idea would be, to have also Brashmonkey Spriter export. So your tool could be more handy for other animation software as well.
But I guess, it is more complecated because of the missing Setup pose. And Spine is the best option here.
I like the idea of the software very much. Keep it going. Kind regards.