Currently the only way to mend an item it by using an aura cache on the altar first, then crouching to mend the items. While this is great for an on-the-go setup, it doesn't lend itself to an automated setup.

My suggestion: Allow items with Nature's Mending to be used on the Natural Altar to repair them directly

This not only makes it automatable, but also allows players to mend their items before they may have an aura cache (though without the convenience of using it on-the-go)