I feel like most games in this jam would either let you scale the player or scale some environmental elements, but I thought it was cool that you could fire the guns at the character to change its size. I kind of thought the tutorial was kidding about that at first!
But I didn't feel like there was a strong reason to go big mode. As an obstacle, the spikes pose a much greater threat than the blocks, and you need to be small to jump over them. Plus, while you can break the blocks if you are big, you can also knock them over or just jump over them if you are small.
Still, I think there is a lot of potential in expanding this idea further!