Two alternative that don't require users rename their entire networks. One, opt-out via MAC address. Or two, opt-out via geofencing: let me pick my house off a map and type my SSID. Both of these solutions could be automated by a little program that ran once in the user's network. I'm sure the clever engineers at Google could come up with even better solutions if they actually cared about a usable opt-out solution.
While I think that having to change the SSID is a lame solution, the problem with your suggestion is that there's no way to ensure that the person opting the networks out actually has control over the network; it would take minutes for 4chan or other mischievous people to opt-out whole neighborhoods.
It depends on why you want the information removed. If it's because you don't want it publicly available then fine, but you may not want Google to store that information at all. In that case opting out is giving them even more information about you; as you'll be potentially linking your IP, Google cookie and account to your SSID when you complete the opt-out.
Google did indeed make a massive cock up over collecting the Wifi data - and taking them to task on that is a good thing.
Demanding a magic opt-out of public data seems to be a case of privacy gone mad.
First we had PC. Now we have privacy. What is it about these things that always get taken to the extreme. sigh