Currently calling interactive_open_or_new will use the last path opened. I would prefer if I could set the default file path to the currently open buffer. The operation is called using a Command_ID and is a bit opaque, so I am not sure how I would go about doing this.

If you're okay with writing your own wrapper commands then take a look at directory_set_hot.

What you want to do is get the current buffer's file name and extract it's path and use that to set the hot directory before beginning the file list.