It's pretty obvious what part II will be, considering Part I is basically arguing that a full, ground-up, greenfield, throw-away-everything-and-start-from-a-bli

It's pretty obvious what part II will be, considering Part I is basically arguing that a full, ground-up, greenfield, throw-away-everything-and-start-from-a-blinking-cursor rewrite is an expensive mistake. Half the comments on this thread have already alluded to it: A careful, piece-by-piece replacement, delivering the new system incrementally (running in parallel with the old system if need be.) Or even a gradual refactoring of the original code base if the base technology wasn't the problem. Read the success stories in this thread - you'll see they tend to follow this pattern.