I wish you luck this year!
That's just a picture. That robot may look flimsy (It really does) in a picture, but look much stronger in real life.
If you can accept my advice, I would protect the battery cable more (If you don't already have some type of cover for your 'bot). Any arm that gets entangled with that cord can snap it, and there you are, sitting on the playing field, with no power. Trust me, I've seen it before, and it's not a pretty sight.
Judging from the pictures, I see you are using pneumatics for your stacker/ lifter. This is a very good idea, and if FIRST took away pneumatics, I don't know what I would do.
Like I said before, good luck this year.
That stacker/ lifter actually looks like a VERY GOOD design, and I believe it will work VERY WELL. I know some serious thinking went into it. I also see that you are capable to go under the bar. It's good that you learned this now, since it is very important to be able to navigate the ENTIRE playing field.