I made this display cake with about 750 wafer paper hydrangeas and leaves. The stems were gumpaste.
Since it's winter here the humidity is really low, and the wafer paper flowers were very brittle. Even though I only attached them to the cake at the very center of the flower it would still be a miserable experience cutting it if it was a real cake.
The good thing about gumpaste is that it's pretty obvious that you need to remove the flowers from the cake before serving it. Wafer paper isn't the same. If it's stuck to the surface of the cake people will assume that they should eat it.
I've written about this before (I think). When you put a lot of wafer paper on a cake it will stiffen up if it dries out or if it's been wet and dried. If you try to cut through a layer of wafer paper ruffles it's going to be like trying to cut through layers of dry, crackly pasta or something. Nasty.
If I was going to do a cake that had wafer paper on the outside, I would cover it with something that could be removed before serving it. That would eliminate the layer of hardened, stiff wafer paper and would prevent the poor unsuspecting customer from getting a brittle mouthful of hardened potato starch.
For this particular design I was thinking that I would probably take a strip of modeling chocolate to wrap around the cake, then attach the decorations to that. It would basically act like a slipcover that could be removed. Then you could glue stuff to the outside of the cake without worrying about how nasty it's going to be to cut.
You can get the wafer paper hydrangeas in my Etsy shop here: Hydrangeas