As I think I said before, a cellulose-based exoskeleton would not be disabling nor need to be shed because it's flexible--there would not need to be any dramatic changes in musculature from the soft-bodied larva--and it can grow without shedding, as seen in tunicates, real world animals with cellulose-based exoskeletons. Therefore, a continuous growth of cellulose plates or thickening of existing skin into a cellulose-based exoskeleton would be realistic.
Also, I just noticed, the art of the larva is actually completely inaccurate--cloudswarmer larvae (at least of this side of cloudswarmer evolution) have 4 flippers, not 2. The artwork for the cloudswarmers genus group is inaccurate and depicts another annoying case of "atavism larvae".