I ran into the same issue and same disappointment!
Fortunately there are some work arounds:
-when brewing ales, controlling ferment temp is really critical in the first few days. After that, as long as you are INCREASING the ferment temp, you should still get a really well attenuated ale with controlled yeast character and no fusels. So, for example, if you have brewed a Vienna lager, and fermented it low and slow around 50* for 3 weeks, then want to lager it, you could pull it out of the fermentation fridge, let it finish up at room temp (it will also degas/push out any sulfur), ferment an american pale ale in the fridge for 3 days or so, then pull the APA out and let it finish up at room temp (hopefully around 70*) while getting the vienna down to lagering temps. I’ve had good results doing it this way.
-The other thing people have done (though I have not) is to interrupt the lagering period to control temp on an ale (again only the first few days are really critical), the crank the freezer back ‘up’ and get the lager cold again, and remove the fermenter with your ale in it. The added benefit of this is you could throw the ale in the lagering freezer and serve from there with a picnic line or faucet (ie using your serving fridge as your lagering fridge).
Ideally, two fridges are ideal, but space/cash/wives/girlfriends or a combination thereof do not always permit.