Not sure I can understand your request in first place. This is my try: convert multiple painted layers to Smart Object layer. Once you want to reseparate them right click on Smart Object layer and choose: Convert to Layers.
You could select all layers and then right click and select Smart Object. This will make one layer, but as a Smart Object. When you want separate layers again, you need to double click into the Smart Object and your layers will open in a new window.
Okay so I know there is not a way to paint multiple layers at once. But is there a way at least to merge layers and then quickly resperate them without having to do selection and then cut>paste>as a new layer or could i select each one and cut them and then paste them into all individual layers?