Hello-
Yes, I have done something like that. I ended up using math to figure out the relative week number (as in not the function that will give you the week of the current year) so that the rotation doesn't skip back to the beginning every year.
From there I just have a switch string that sets the extension for the call redirect step based on week number. That's not to say you couldn't do something similar using an XML document.
To make like a bit easier when you're working on the solution you could set the variable in the Call Redirect step as a parameter and only change that piece rather than changing the script that you're using.
I Hope that helps.
DJ