They're not so much "innovations" but rather just frugal decisions in my opinion. By doing the quarter for a cart thing they insure people return their carts to the front without an employee. In other stores an employee just goes to collect them from the lot. By allowing people to take the boxes you reduce the number of bags used at checkout and you need less employees to remove the boxes from the shelves.

These aren't ground breaking ideas, they are things which make sense in a capitalist world to minimize costs while being efficient. That said they are also contributing factors to why Aldi feels like a discount store in comparison to other stores. As a consumer I don't mind the extra hurdles going to Aldi evokes, but if I'm going to Aldi I already am taking a step down in "quality" by US terms.