I really like how this design has progressed from the original Reverse Stacker concept. I would recommend changing a few things on the overall robot design though.
For one, even if you used string to hold said amount of cubes, what is the guarantee that they will stay in that position? The cubes are extremely slippery from what I’ve heard, so unless you try to swap those out for something like latex tubing or a long strand of bands made from cutting up a few, I feel that it would not be able to consistently stack up that high.
Another gripe that I have as @MyrddinEmyrs mentioned is the center of gravity on your robot. The first 4-5 cubes or so would be fine to stack with this robot, but after going past that, the robot will most likely tip from all of the weight being at the edge of the robot. It might be solvable by placing the brain and battery in the very back of the robot, but it will only help so much. If I may recommend, having anti-tips in the front that do not prevent stacking in the goals would be the best option in your case. Lowering the overall base height also may help in dropping your COG.
This final opinion might be a bit nitpicky, but I feel that alignment with this style of intake would be seen as fairly hard unless you design a passive aligner that does not interfere with out-taking and placing stacks in the goal. if anything, trying to make a dual-stage intake where there are side-rollers to help move the cubes to the main passive intake might be more logical for driving smoothly and efficiently.
I hope I see this design progress even more throughout this season, good luck guys!