I’ve been developing a cairo-based canvas for GTK+. Maybe you want to replace GnomeCanvas with it. If you need help with porting arbour, or there’s something missing, just contact me (either per email or through libccc’s bug tracker).
I’m not a coder, but I know the decision to switch canvas has been made. Candidates so far are GooCanvas and Papyrus. I guess it would help if you could offer a comparison to the 2.