Are you using the plain Flash runtime or the Starling runtime? In any case, you can create a custom texture loader based on the default one spine-runtimes/FlashTextureLoader.as at master. You can then set it on the atlas so it gets used to load your textures from a different source like here spine-runtimes/Main.as at master
As for attaching a TextField or DisplayObject to a slot, you can modify the SkeletonSprite class which goes through the skeleton's slots in drawing order and attaches them as children on the SkeletonSprite. Simply add a few lines to specify which of your custom objects should go on which slot and add them as children during the slot traversal spine-runtimes/SkeletonSprite.as at master
