I guess this is platform dependant, but would an "open file with Decker" in the packed version (or .html/.deck file as an argument to the binary) be the same as dropping a deck onto the editor? One way of quickly "opening" a deck could otherwise be to simply "open" the file by doubble clicking it in Finder (or other file browser).
(I do find the "drop deck on window to add resource" very intuitive and personaly don't see the need for "opening by dropping" if I could do the above.)