It will not be big enough for a 4 gallon boil as 16qt = 4gal. Not enough head room to prevent a boil over.
Many stainless pots are quite light, especially the inexpensive ones. As long as you take it off the flame when adding LME or any thick liquid, and keep the liquid stired until the LME it is completely disolved, I don't think scorching will be a big problem, though it can happen with any pot.
Beer is like porn. You can buy it, but it's more fun to make your own.