Stranger things can be seen. I had a student who was severely pigeon toed and his toes literally pointed inward about -15/15. He physically could not ride duck or anything approaching a 0/0. We tried a few things from -9/12 and finally found a forward stance with the front foot at 3 and the back foot about 21 worked best for his condition. There are lots of medical issues out there and you will see some pretty strange shit but hey, whatever works and gets them on the snow having fun.
i'm about to go +9/-15 after trying out my gf's board which is set up goofy +15/-9.. fixed a problem i have with.. slightly longer lead leg (maybe like 3mm). makes it easier for me to transfer weight front/back. within the first run my riding effort went down and everything felt more natural. guess the point is try different things, might be surprised at the improvement it makes.