I agree with those who say we go the generic route. The original story is well within the public domain, so there's no reason why we can't just make new material inspired by it. While Glenda's dress from the movie is iconic (absolutely beautiful), I don't see why we can't just make another dress as equally lovely beside it. Geobra knows that Playmobil is beyond capable of doing it, as they have a bajillion different designs for full skirts and such already. The wicked witch should be easy as they reuse their face from knock off Maleficent or just straight up "greenify" existing heads like they did with Frankenstein's monster or Mr. Toothache.
I believe y'all already tackled those monkeys beautifully already though.
Related/unrelated I also have a flying cat made for me by MsOmega that uses the crow wings
Halloween Castle 2012 no11 by Tim, on Flickr
But if Playmobil were truly to do it, maybe they'd use a model much like the new demons coming out, or the old Super 4 Mysterios to create them? Perhaps the wings could attach to the vest (they did have those right?) like fairy wings do. Just make sure to give them tails! Monkeys aren't apes!
As for the ruby slippers, I think the best route for this could be those wonderful new clip on shoes (always wanted Playmobil to make those!) with glitter added to the plastic. That way they can be added and removed without having to change the whole bleeding legs!
For the lion, I'm torn between just using a plain ol lion with options to put ribbons in his mane, or an "anthropomorphic" design akin to the tiger trick-or-treater from 4770.
For buildings....I'd be in heaven!
The village and yellow brick road would be WONDERFUL for a fairyland diorama. The witch's castle could be a repurposed 3665 (all hail Steck!) and the Kansas cottage could be a welcome addition for Western too. I just hope and pray they'd keep the faces generic and not go the Ayuma or Dino Rise route with too different of faces and body types. That way we can still have that glorious option to customize!
Siiiiiigh. Why do you people give me so many ideas....