Has there been any discussion regarding different file export options for captioning? I'd like to have .cap option if possible, or another file type that allows placement data to be recorded in the exported file.
You are correct that PR has no caption export format for Subtitle format captions that contain positioning. The only current options are to use one of the closed captions (e.g. EBU), exporting .xml or .stl. You may be able to convert to another format from there.
There has been the most support for .vtt as an alternative.