@[deleted]
If you have a lot of equipment, the sample above may not be the complete solution for you for the reasons you described.
I'm not sure where you read "all atlas pages will be loaded to the memory".
I think this is only true if the atlas material and Spine-Unity AtlasAsset are used.
There are a few ingredients to ideally make your case work:
You need to be able to pack a texture at runtime (to reduce draw calls and not need to load everything). I think Unity has this built-in functionality through code, separate from the Unity Sprite packer. I think it's a code-only thing. You should look up how to do this.
You need to know how to create attachments/skins at runtime, just from knowing atlas information and UV coordinates of equipment images. There is a forum topic on this, we'll look for it.
3a. If you want to use Spine editor to define all the unique alignments, there may be a need to modify the loader to permit loading attachments (or skipping attachments) if you don't have all the atlas information ready at load time, and load them later once you have the necessary material/texture/atlas information. This is also necessary if you want to define everything in Spine editor, but, say, want the equips to be as downloadable content.
3b. If you don't need/want to use Spine editor to align hundreds of equips images, and can make the equip images loosely-uniform in shape and dimensions based on a few main shapes, this will be a lot easier for everyone in this pipeline (artist, animator, programmer) AND it won't need any modification to the Spine code.
On PC though, you shouldn't have any problems.
Assuming you were crazy and have 100 (1024x1024) atlas textures just for equips.
Each of those textures actually take up a little under 5MB of VRAM. So you have a little under 500MB of VRAM for those textures. This is some even old graphics cards with 1 or 2GB can handle.
It's not ideal, and I don't think you should ship with such an absence of optimization, but we can work toward this piece by piece and you won't be blocked with other things.
It may be a little slow to load 500MB worth of textures into your graphics card though. But let's assume you don't need 100 atlases while you're still in the process of developing.