I finally overcame my fear, but oh boy, was it justified!
This is what i wanted to try.
At first the leave wasn't that hard, but i was under the impression, that paddingcord was used. Trying to introduce it was a nightmare... Reread the picture, came to the conclusion no cord was needed. Several tries later i succeeded in fabricating something that looked like the picture:) Only my leaves were bigger, but what the heck.
The only flaw of the pattern was, that the leaves are only connected on the top and bottom, kept curling up. If i used the stitch like that in my cardigan, they would curl out of shape even more.
I had to come up with a solution, i improvised two attaches on the side as well.
Here's a detailed photo of the leaves in my freeform cardigan.