I just should say that I am not succeed to provide really safe ghosts. 

If you will try to implement new kind of proxy (on top of Ghost) it is possible to hang image. 

Problem that when you make some mistake in implementation it usually lead to infinite recursion and interrupt usually not helps because opened debugger produces new messages to ghost which produces another recursion due to original errors. And errors are not only exceptions but some unexpected messages to proxies. For example if you will use Set to implement proxy behaviour (for some reason) it will send #= and #hash to proxy when you will try to add it.

There are tools now to minimize such cases. For example standart meta level will not intercept messages from debugger. But as soon as you start experiment with empty meta level you will  get such problems.

This week Guille Polito start to use Ghost for new proxies and he was not happy due to this kind of problems. Maybe together we will find some solution how to make ghosts safe.