Wilson, there is a somewhere where the sacred circle is complete--Smalltalk. The commercial Smalltalks allow nearly effortless version control with tagging, branching etc at all levels, from individual methods all the way up to entier packages of classes. Completely integrated with the code browser. Squeak and Montichello aren't quite there yet, but it will come.

And since in that place the design is the code plus (automated) unit tests, life is good. If only you could get there from here...