For those few like me who enjoy min/maxing only to a point and so still prefer Sheds to Barns for fermenting, here's what I'm pretty sure is the max possible fermentation vessels. You can shuffle around where the pathways are but the number of fermenters I think cannot be increased, and that these pathways as-shown involve the minimum number of tiles to traverse in the course of executing a swap. For those stuck on mobile like me, I've also included what I'm pretty sure is the optimal layout given mobile's inability to harvest diagonally (even though we can place and fill diagonally!!).

I wasn't aware that mobile couldn't harvest diagonally. That's... yet another reason I'm glad I play on PC. You've shuffled them around, but yes, you've hit upon one of several potential maximum number of artisan machines per shed designs. You can see more information on the wiki.

Unless I'm counting wrong, it seems like you have 67 in that first picture? I'm pretty sure it's not 70, anyways, since the two sides are symmetrical plus one extra one in the middle (across from the door), so it should be an odd number.

You are quite correct; I was wrong and must have mis-counted. I apologize and have deleted my message about it. I really am awful at numbers (initially I counted pathway tiles then subtracted from the total area; instead, prompted by your post, I re-counted a few times using the items themselves).