IMO- If your character can walk a distance, they can shift that distance. This means not through doors, walls, windows, etc. UNDER ANY CIRCUMSTANCES. You're not the flash, people.
Secondly, I'd like to see combat scenarios as well. What happens if they try to shift through a weapon or other type of magic thrown at them? I personally think this should work in the sense that, they could do it, but it'd hurt. A lot.
This is very nicely written, and would be a good compromise to the blinking dilemma. If, and only if, people stay within the boundaries.