Can the Samsung Galaxy Note II stock camera app be transplanted to a custom firmware?
The short answer is no.

The detailed answer is - it will be difficult - very difficult.
The camera from the stock samsung firmware relies on the touchwiz framework to work correctly. Any AOSP based rom comes without the touchwiz framework - and that's one of the best reasons to install an AOSP based rom. 
So what does this mean in the end? 

You would need to modify the application - include the shared libraries and may have to port the framework - it won't be worth the effort. If you're not happy with the stock camera application, try one from the play store - they might even make better pictures.