I haven't found a practical use for g200. If Uxx.xxxx Wxx.xxxx is a safe place to change tools then why not make that your tool change position. I use G53 for my tool change position. All you have to do is jog the machine to as close to your part as you can get with your longest od and id tools like you said then look at the position page and use the machine coordinates as the tool change position. Example: the safe position is X-3.1 Z-5.3. It would code like this:
G00 G53 X-3.1
If any one else can give me a reason why if Uxx.xxxx Wxx.xxxx is a safe place to change tools, we are letting the machine continue on it's way home (G28), let me know. For you people with the bigger lathes this seems like a real waste of time.