Whoa, even better! Very nice! Man, you just came up with a solution to something you probably hadn't even thought of with that external app of yours - a way to open up a file in the program you want, regardless of creater/code or file extension. That's something just about everyone using OS X has been grumbling about - there's no easy way to get a certain file (or files) to open up in a certain app. I'd say go for the external app, even if you do figure out how to tell the Finder directly how to do it. It would make life much simpler for lots of users!
Plus, programmers could take advantage of the app to use as their open/save dialog instead of the standard ones. I know I would.
Oh yeah, and I know Carbon apps can have nibs. I tend to think of these as "unamed hybrids," though. They're not straight Carbon apps anymore, but they definitely don't have anything to do with Cocoa, either. 'Course, I wasn't thinking of that when I said it, but the Finder doesn't have nibs, so I'm covered.
