Did you check out that Nail Geek hack I gave the link for?
With your BB code idea, though, you have me thinking.
What would be a good identifier to insert in the tags though? Ideally it'd be the actual ID of the image (because the image names, etc. can all change at any given point by the ID never would)..... but it looks like in your mock-up above you may have taken that into account already.
Free thinking, it would tricky but not impossible.... a new BB code that fires off some PHP code to grab the thumbnail link from image ID to generate an inline img tag and then in Gallery a change to the template for the new row to display the image ID. My only initial concern would be possible overhead that having a bunch of these tags in one thread would do. HHmm....
(Kevin wonders off to his lab mumbling something about trying to remember where he put his PHP BB code test from ages ago.....)