"bot that blindly moves an entire File namespace from one wiki to another" - no, that's not on the table or something i'm trying to propose. but i do understand, that this concern would become reality no matter of my or your intentions.
well, why developers provide an API to their services? so that other developers can build some apps on top of that.
about the "what's the problem" part - currently one can mostly do it "randomly" (via articles) or going through some category, where there isn't guarantee, that user won't be presented with files, that somebody has already looked through or otherwise clutter not-yet-looked-through-images. ok, you can so some fancy things (intersections and so on) with Petscan, but I would bet, that many, many users don't know about that. And it happens in "old fashion" way - new filepage is opened in new tab/window etc.
the "proposed solution" (the tool) would contain list of images, that should be good to ex(im)port and presented in SPA-like environment, so that user won't need to go outside tool to make actions. mainly - workflow improvements for power users. something like this.