Chiming in here as I’ve had some experiences with ordering custom Bauers recently that might shed some light into what’s possible.
Customer was in a car wreck that caused his one leg to be almost permanently swollen. Knew this was going to be a tough fitting, so right off the bat I told the customer I’d like to get some additional eyes on his scan/foot. Sent the photos to Bauer and got the feedback I was looking for. Went ahead and ordered the skates and quicker than some other customs we’ve done, they arrived. Fit was absolutely perfect. Turns out they were able to almost retrofit a size 10 Fit 3 onto the midsole/outsole of a size 8 boot to give the customer the volume he needs, especially around the ankle. The results were incredible. So as far as getting a “Fit 0,” it does seem like something that could be possible however you definitely need to have an experienced fitter who can ask questions like this. Pic below for reference of the skates. His customs are next to a retail size 8 boot.