mipmaps are just the lower res textures created from the original. its done by the engine, you can turn it off and on at any time without having to reimport. they play another very important role in helping reduce texture shimmering when the model is in the distance and reducing the texture memory needed. no matter what size the base texture is, it will still mipmap.
including all levels as a separate texture will just increase the asset size for no reason.
if the customer decides they do not need a 4k texture. they can set the LOD bias in the texture to something higher than 0 and it will reduce the mip level to a smaller size texture, and when they package the project, only that level will be packaged.