Idea Summary
The Javascript item interface should have a way to toggle whether an item is required. 

Use Case
Occasionally the value of one item determines if another item is required or optional. For example, if Beverage=Beer, the Customer Age field may become required. I can add post-submit validations for this, but there's no approved way to change the required appearance of the item. Right now, I just toggle the is-required class on the appropriate container.

Preferred Solution (Optional)
I would add apex.item.setRequired(boolean). There are already enable(), disable(), show(), hide() functions, so adding require() would also work, I just can't think of a good verb for “not required”. Unrequire?