You will have to include a fair bit to generate a sprite collection atlas at runtime. While its possible, I wouldn't recommend it. All of the tk2d runtime is pretty lean, whereas the editor code allocates a ton of memory. Wouldn't it be possible to generate the atlas it self on the server?
Failing all that you could probably try Texture2D.PackTextures to pack the textures, and then use the runtime sprite collection stuff to set it up. It won't pack anywhere near as efficiently as tk2d though.