Did you read the comments at the links you list? People are saying that Common LISP was doing both at the same time in the 80s. One of them even describes what can go wrong when you do it badly.
Here's just one of many: > Common Lisp can change pretty much anything at run-time. If you redefine a > class to have fewer or more slots, the existing instances of those classes > will have some problems. Another:
