Wow! you have created the prefect systainer trolley in my opinion!
I had designed this exact modification already in my head, but never acted on it because I know I would never execute it even half as brilliantly as you have. I assume the wheels are a little higher than standard, but looks like she would roll ok. And importantly you've got the back of the systainers flush onto the frame.
Nice job! I'm genuinely jealous, I want one.