And why did it happen, anyway?
Would need a really good reason for it to work...
What about doing the opposite, muggleborns suddenly abound while wizard couples amount of squibs skyrocket...
1. At the end of the first year, some strange blagoonga resulting from V.'s shade trying to possess HO instead of running away and Harry stumbling back into the Mirror, he gets moved about in space (the US, perhaps) and time (say, to 1970). The next time he appears in the UK, he is thirty-something and...
I have read something vaguely like that at least twice. Not using that specific plot, but using a plotdevice to put him elsewhere and return grown up(or with a grownup mind at least).
One was good one was bad, so it certainly has potential.