The best way I can fix this puzzle overall is to make sure that the twins stay awake for a certain duration instead of being knocked out after the contraption completes. This is where the "delay" feature of goal setting would come in handy. Time how long it takes for the wrecking balls to KO the twins from the start of the simulation. Take that number, round up, and add 1-3 seconds (or more if you prefer but don't go too long or it will feel the puzzle never completes). Make sure to mention they need to stay awake for x amount of seconds in the description. Also the balloons are exposed to lasers so make sure they can't be popped. Also the device part of the lasers make good shields so be careful of that.

Twins saved with just a blue laser and laser splitter. I had just enough coord to be able to do just that from the outlets below. For this particular exploit, make sure that there is enough obstruction where I can't do that anymore where the length of it is greater than the maximum coord length.