There are two problems with that, exactly the same as with Camino. The one is general - does Galeon support some extension scheme? Like binary plugins with access to the user interface? Is it documented somewhere? The other problem is my own - I know almost nothing about Linux programming, so getting this done might be difficult.
Same thing as with Galeon - Camino has a native user interface and doesn't support XUL extensions. Maybe it has some extensions mechanism of its own, but even then the extension would require native components and I know next to nothing about programming user interfaces on OS X.