Primarily the need is for another app to issue a osascript command
to "open this file in the current window" at a new pane in the
bottom - it will never get more complicated than that.
If it's a single, fixed behaviour and isn't intended for end-users,
I'd suggest doing the quickest and simplest thing possible. Use
NSAppleEventManager to install a custom event handler that takes a
file ref as its direct parameter and performs the whole operation. No
sense in doing extra work to implement a full object model if
nobody's ever going to see it. Wouldn't even bother listing it in the
application's dictionary if it's just for private use.
Easy to forget that Apple events aren't just for human users. :)
