I would like to request the addition of an "Open with…" whereby I can open a RAW file (say a NEF) in another Raw converter and do the develop / process in this app. Then save say in TIFF and return to the Adobe environment, to continue work on this externally converted file.

In the case of a NEF I would (in an ideal world) "Open with…" Nikon ViewNXi/ Capture NX-D, do the Raw conversion, then export a TIFF back to Lightroom/ Bridge.