As with nearly any new feature, there are many ways it could be done, each with various trade-offs. The way we chose makes it easy to display frame-by-frame animation. Your idea would require creating an attachment for each frame. That gives some additional flexibility, for example allowing each frame to be positioned or to use a different mesh. However, it is more work to set up, needing many individual attachments to be defined in the tree, in exports, and in memory at runtime. More importantly, it would mean you'd need to use a slot for each sequence. With our approach where the attachment is the sequence, you can have multiple sequences as well as non-sequence attachments under the same slot. This fits more closely with how attachments are used and especially how skins work.
Note in the GIF that there is no need for the other right-wingXX attachments. Those are there only because the existing dragon skeleton was modified for the GIF. You only need a single attachment for the sequence.
