If you pump a UV out of an action and pipe it into the action where you are using the deform mesh you can parent the UV to the deform mesh, as well as the plate, and pipe it out in a separate output. Then take this deformed UV into another action and apply it to the original plate. Then you can run the effect slider on the UV to increase or decrease how much deformation is happening. That way when your client says, “I like the way it looks but lets dial it back 50%”, you can reduce the effect on the UV to 50 instead of starting your warps over again with 50% less warping. Also good for animating warps on and off.
I also use UVs to separate out different parts of the warp. Instead of warping every part of the face with one deform mesh, I might first start with neck and jawline work apply it to a UV using the method described above. Then pipe that deformed UV into another action with a different deform mesh for the nose and apply it to the UV. You can keep stacking warps on top of each other this way and apply them all with one UV at the end. That way when the client likes the jawline, but not the nose, I can adjust one mesh without having to deal with the others.