With A medium, you could replace the short rifle with a high power/accuracy AR; or you could replace the SMG with a shotgun or an AR with a high fire rate. I think you would have more luck that way instead of using 2 light weapons.
Light rifle because I love using sniper rifles, SMG over AR for the the equip & reload speeds and overall lightweight nature. I'll wait and see how the speed stats fare at release though, I may very well swap to an AR if the drop isn't too noticeable.
Besides, just because a body type CAN use heavier weapons, doesn't mean it HAS to. :thumbsup: I used a heavy armor/SMG build in MAG and it was a CQC beast, as I said, I'd like to see how it performs here.