I tried that on my Hawkeye so he could do more accurate draw on his bow.
Arms are a little big for Hawkeye(Although i am perfectly happy with the figure), but would be perfect for Superman if you have the two figures to do the swap(It's very easy to do). Another way to go is to sculpt on some extra muscles yourself. I did this with a custom Superman figure once. I went absolutely roid-rage-bananas with mine, but it's possible to tone it down a bit.
Here are pics of the terminator arms/TTM19 mod:
You could have just gotten the Wolverine Last stand body or the Joe Colton body and you would have saved yourself all that work.