Being frustrated about the many changes to farming lately I decided to list my suggestion here instead of cry about the current system and not offer any alternative.
I like the idea of the worms playing a bigger part as in real compost having worms is a huge help. I like that any crop going in doesnt matter on purity as worms eat anything. I would change that meat should not go in as most composters know that meat can create disease. The purity of the wood and nails made to make the compost seems silly as it doesnt matter what you put it in as long as it gets air and water.
I would require rotation of crops and plowing of fields to help boost purity. Then we can introduce Oxen, horses, and dogs. Each can be used to pull a plow of different effectiveness. (metal and wooden plows) They should also have phlegm that needs food to replenish. All three of these could also be used to pull carts. making moving around a lot easier. Taking it further would be how you tend to the field. Maybe have weeds grow and if you weed every day then the crop will be more pure. Also if you water and add fertilizer everyday its helps the purity as well.
Im sure someone smarter can come up with good formulas for what should effect what. But I think it would make people happy to introduce new things to fix purity issues than just to keep messing with current things and angering everyone as we never know whats going to be good. If adding purity to wood is important to you then make it as a source of durability for the things you make with it but not the purity of things that are put in it.
Fuggles