I guess they thought having the digital depth gauge was enough and you would just stop at a number. Warco web never gives you enough data to see if the digital depth thing can be zeroed or set to a value.
Anyway you could consider a rotation stop on the main feed lever like on some drills. Limits you to 1 rev but possibly the easiest. It looks like there is too much casing around the quill to follow the common milldrill practice of a collar on the quill with an arm and so on.