Not sure what your motivation is, but just always keep in mind that there is no true destruction of data if you keep your original raw files. Sure, you could do stuff to pixel data converted from them that might be considered "destructive" (which is a misleading term I dislike), but you can always go back to the raw files and just do it over again.
"Doing it over again" may sound wrong to you, but assuming specifically what you describe is even possible, a computer with power enough to do all of what you describe non-destructively and quickly enough to be acceptable might not have been invented yet. It sounds as if you're wanting to tweak conversion parameters for a whole set of images then immediately see the results.
I'm guessing it won't be completely possible, because at the very least there will likely be a need to "Stamp Visible" (i.e., a step that has to be redone after having changed conversion parameters) so as to be able to provide a pixel-based image to the Nik plug-in. So what you may be seeking is a workflow that requires minimal rework (vs. none at all).
I'll be interested to hear how this plays out.
My thought was it would be good if I could tweak RAW conversion settings after making edits to the image without having to re-do those image edits, or tweak someting in Silver Efex after making image edits.
Adjust your raw files in Lightroom or Camera Raw, and send them into Photoshop as Smart Objects.
Stack the SOs in one Photoshop document.
Auto-Blend Layers will not process SOs, so duplicate the SOs then rasterize the duplicates.
Auto-Blend the raster layers to generate focus masks.
Drag the masks from the raster layers to the respective SOs.
Delete the raster layers since they have served their purpose and are no longer required.
Target all the masked SOs and convert to a SO.
You now have an SO (containing several masked SOs) that Silver Efex can be added to as a Smart Filter.
That SO can be double-clicked in future to access the masked SOs, and each masked SO can be double-clicked to open its contained raw file in Camera Raw for new adjustments.
Wow, that's so crazy it might just work!
Actually, that seems like an efficient, great way to get what I want. Thank you! I'll give it a whirl and report back.
Conroy may well be onto something. I'll be very interested to hear how quickly it responds to changes.
There's a serious flaw in my suggestion which will probably make it useless. I didn't consider that the Auto-Blend can change pixels in order to achieve its result, and not just create masks.