It's certainly a reasonable suggestion. We could show a dialog with the image files, maybe with type to search/filter. It would make sense to have a way to set either the name or the path.
In case you missed it, you can drag an item from under Images to an existing attachment to rename it. Dragging and dropping isn't as fast as a dialog would be, of course.
Most often Import PSD (see blog post) or Import Data is used to bring images in as attachments that are already named and placed in the right position. This skips a whole lot of tedious work that has likely already been done in your image editor. The next most common way to create and name attachments is to find them under Images and drag them into the viewport or to a bone or slot.
Given that, it's relatively common to type some variation of an existing name, but I'd say it's not super common to type a full path (or choose a path from a new dialog). When doing it en masse, find and replace makes sense, as you mentioned.
I see in your screenshot you are doing it to set a path for a linked mesh (you could also rename the linked mesh). That makes sense and is a reasonable workflow, though probably you are typing a variation of the existing path rather than retyping the entire path.
We'll consider a dialog for setting the image path (and region/mesh attachment name). I've created an issue to track the enhancement. You can see all the issues on our roadmap:
http://esotericsoftware.com/spine-roadmap
Lastly, it's worth mentioning there's a workflow where you don't need to duplicate attachments in Spine that differ only by name/path. You can set up template attachments in Spine and then duplicate and configure them at runtime. This allows you to create many hundreds or thousands of attachments just by creating the images, without needing to rig them all in Spine. It makes sense for large projects, but the overhead to set it up may not be worthwhile for small or mid-size projects. More here:
https://esotericsoftware.com/spine-runtime-skins#Creating-attachments
