
As you know, the highest quality clay is bone clay. Potters clay was implemented as the most difficult to craft. But now it can't be better than bone clay. Now it is needed only for a minehole.
I want to propose a new implementation.
Let's put into game new clay - Earth clay. Crafted by potters wheel. Formula is (((arc + gray + mulch + brick)/4)*3+potters wheel q )/4

This clay is crafted from those clays (arc and gray) that so far play almost no role in the game. So it is good chance to back their significancy.
And adds the need to improve the quality of trees and potters wheel. Also mulch will now be more important.
Potters clay will be mixing of (((bone + coade + earth + brick)/4)*3 + potters wheel q )/4
This combining of top 3 type of clays and quality of potters wheel will give a big chance to make it the best clay in gaame. Not so much, but best.
And it makes it necessary to keep all 3 types of glue in good quality.
The most difficult glue to craft must be the best!