oh, i am VERY interested in this!
seems like it'd be a very handy tool for modding, since file conversions are usually either done through gimp, if it supports the format, or some random ass tool/website that does only one thing...
having a swiss army knife type solution would be excellent!
one point of feedback about the interface:
anytime there's a slider, there should also be a direct input field to type into.
this is to prevent things like UI scaling, or mouse sensitivity preventing proper input...ask me how i know...
might also be an accessibility thing; for example people with tremors, or generally low dexterity.
text input is never the wrong choice, but sliders can be!