I have an idea for a PS feature. It would be great if I could create an action from a selection of layers. Think of it as recording after the fact. PS has the history information, so I think that it wouldn't be too difficult.
Sure. Think of it as a sort of LR "Sync Settings" for PC. The user edits the shot as they normally would, then they want to create an action (saved settings) to apply the same edits to other images (think color grading, etc). The user would select the layers from which they want to create the action and then via some menu option (Layer -> Create Action) it would save the steps that created those layers as an action.
Ok now I understand. But how would you know what should be part of action? Name? Blend mode? Masks? Layer effects? Smart filters? Would it create whole layer for you? And you care only about adjustment layer settings you can use presets. But is in each layer separately and I am not sure how batch processing could deal with it.