We must be entering a high-magic zone, cause you've just described exactly how I was thinking of implementing it.
If the PBW people were not too put off about it, I would have them change the data files every sunday or monday.
I was thinking of manually generating the altered files, so it would be easier to make pattern changes like I mentioned below.
I was not really concerned about implementation, more playability. How would you feel about having your WMG dreadnaughts suddenly become impotent, and never being at the peak of technology.
It would be like the price is right: the highest tech without going over is the winner
and you can only guess at what the right tech level is going to be next week.