I mean, we are put into a situation where if you want to go into melee, you HAVE to do stealth initially or get cut down by bullets. I wont even get into the shotgunned mini nukes, there needs to be a minimum distance enemies fire those damn things. Riot shields, junk shields, etc. I mean, is it that much of a leap to have someone take some scrap metal and piece together a shield for himself if he knew he was going to run into an enemy sporting a submachine gun?
They could be one of the other durability items like the power suit, each shot it takes busts up its HP durability, and eventually it breaks and only stops some shots. I just find the lack of melee defense disturbing, and any one handed weapon be it melee, or a pistol should be usable with it. Just makes sense honestly.