with everything formerly worked on there, how would I now implement the new into the old?
It's your game and only you can answer this question. I mentioned before that your system of attaching sprites with dx/dy instance variables and a dictionary was overly complex and error-prone. I understand you based it on R0J0hound's advice - he's a brilliant programmer, but he works in Construct 2, where hierarchies don't exist. In Construct 3, the hierarchy feature would be a much simpler and more efficient solution for your task. That said, you don't necessarily have to switch to it.