I don't see many problems here. You need to be able to weld 18 ga well and not have any air leaks. Also, avoid large areas of flat material as you will have 10-20 pounds per square inch outward PRESSURE in the intake under boost. So, the intake could distort under some conditions. You will have ~10 psi of vacuum at idle (forces pushing IN on the metal sheets) and ~15 psi pushing OUT at full boost.
Otherwise, I'd make sure to paint/coat it with something to stop corrosion, but I think you can handle that no problem.
Lou