CraftTweaker offers an excellent starting point. With it, you can alter properties in-game, such as swap recipe components or change what an item does — for example, make all food less effective for a survival-themed server where you must fight off starvation. You can even...
However, sheep must eat grass from grass block in order to regrow their wool coat, meaning you need a fairly large pen with plenty grass blocks to recover their wool after shearing. If your farm has an enormous amount of sheep, they turn all of the grass inside of the farm into dirt,...