You are now having this conversation on both Flyertalk and Airliners.net and I am sorry to inform you that it won't likely make much difference.
May I suggest you send KLM Customer Care the suggestion though, even if you are most likely to get the famous reply "That is not possible" or "dat is niet mogelijk".

Please also note that often airlines use "local crew" not because of better service to the passenger, but because it's cheaper than the ones hired in Europe.
That may explain the reason for so much local crew on other carriers although I still doubt if indeed all these carriers have Portuguese speaking FA's on every flight to GRU.