Most stability issues are caused by wxWidgets framework. A custom GUI is being developed for the upcoming next release & wxWidgets will no longer be used as it's severely limiting & each update the devs behind it put out seems to fix one or two existing bugs while generating a boatload of new ones in their place.
As far as I'm aware, the upcoming new editor should be a lot more workflow efficient. Not sure on drag & drop capabilities, but it's something I would like to see. Simply dragging an image or group of images into the viewport wouldn't really work that well as you still need to assign images / animations to scene objects, characters, interface buttons, etc.
But aye being able to drag & drop images or a group of images into the image window or into the animation window of the currently selected object or animation would be nice. By the way, you can already import a group of animation frames into an animation at the same time by making sure you name all relevant frames with the same name plus an index number on the end - something along the lines of name_1 or name_01 or name_(1). So you would end up with something like...
test_(1) dot png
test_(2) dot png
test_(3) dot png
Then you can load in an entire animation with the load frame sequence icon (it's the one with the stacked image & little green plus icon).