Do you think it would be ideal to allow a UK couple fresh into the country to adopt a Swiss and German-speaking child... when the parents don't have Swiss nationality or permanent residency, and don't speak any German? For all the authorities know you may be planning to leave again in a year or two, and that would mean a lack of stability for an adopted kid who was otherwise born and raised here thus far in life.

By all means go for it, but I would be surprised if the authorities saw that as anything approaching an ideal situation.