In an activatable class, the constructor that's called by the activation group is currently required to be public. Since this should normally only be called by the activation group, it seems like it would be nice to be able to declare it private.

In a similar vein, if I have an activatable class, and I normally only want to hand out smart proxies to activatable instances, I might want to declare the activatable class with just package access, and provide a separate public class that can be used to create an activatable instance and get back a smart proxy (with the activatable stub inside). However, the activatable class is currently required to be public.