I think that if this eases traits adoption we could remove the  
behavior refactorings and introduce code duplication
instead (ie flattened the traits) so that removing traits could be  
done for people do not wanting them for x or y reasons.
Removing traits is much easier than introducing them because of  
bootstrapping reasons.  We could also have the policy not
to use traits for kernel parts so that only applications use them.

Stef