You might try setting the Global Lighting to 90 (the Angle) by going to Layer>Layer Style>Global Light.
If that works you can record that in an action.
That definitely works, as long as your sources are global. Unfortunately, our practices require that our global lights be turned off. So I want to find a way to set all lights to 90º and to shut globals off.
I don't believe that can done with an action, so might ask over on the photoshop scripting forum and see if a script could do that.
The scripting abilities of Photoshop mystify me. But it's probably worth looking into.
Thanks for the reply.