Probably for the next world, introducing the change now might screw up some people.
But as the title suggests - make potter credo require quarryman credo, not the farmer. Because:
1. Potter is masonry-based credo, like quarryman. It is not farming-based credo
2. Farmer already leads to 5 credos, while quarryman "only" to 3
3. It thematically fits miners, who deal with digging, rocks and minerals, rather than farmers dealing with plants, livestock and organic stuff
4. Finishing farmer credo requires you to have well-established farm and related industry. And potter bonuses would seem most useful before that
5. In the groups I played until now noone took it because:
...a) farmers had other credos to chase and didn't feel like suddenly skilling masonry and digging clay
...b) no masonry-based char was willing to deal with farmer credo (useless for them) just to get potter