What sort of data do you have to show that it saves "considerable" battery? 3% is what my phone reports after 12.5 hours of having the WiFi on (GSam only reports 1.8%). How is saving 1-2% by not having it on all the time "considerable?"
The problem with the toggle is that you have to either set it up to be so short that your WiFi is basically on all the time or you set it longer and have terrible resolution. The cell near doesn't help much because you run into the same issue. You will either end up with bad distance resolution (you'll only know that you're close to the cell tower that's' nearest to you) or bad time resolution (you'll have to wait for your phone to know you're at the more specific location), all to save minimal battery.
You also totally skipped the part where I mentioned that if you're using Google Now with any of the location features on then it seems to be battery neutral. My location is not checked any more often with Geofences on than it is with Geofences off if I have Google Now on. The amount of battery my phone uses while idle with all of this on is about 2% per hour.
Also notice that the OP hasn't complained about battery life while having WiFi on all the time. You're totally missing what he's asking for.