send those back, and do not work with that shop again. also, anyone who tells you 5052 can be used in a load bearing position is lying through their teeth. 6061 sheet definitely exists and is hilariously inexpensive at 16ga. also, while small surface defects are normal, that photo shows completely inexcusable defects. if the sheet edges are that damaged, they should be chopped off as kerf.
finally, you cannot willy nilly paint plates because if you add a couple mils of paint to a 16ga sheet, it will become too thick to fit switches. if making plates with aluminum, grind parallel, finish to 30uin, WJ cut and then anodize. otherwise, the best option for making plates is mild steel. grind to something like a 60 finish, but grind a couple mils under 16ga. then, you can either laser and deburr or wj. finally, powdercoat, as oxidization is pretty uncool.
if given a choice between 6061-t6 or t651 and a mild carbon steel though, i would go with the steel. aluminum is light, but at 16ga, cut for switches, what you care about is rigidity; young's modulus, yield strength and ultimate tensile of steel is about 3x 6061 sheet, regardless of temper.
stainless is obviously an option as well, and we have a great source of stainless plates on the forum. however, the list of shops that can grind and cut stainless is short, to say the least, and it's going to cost way more than dealing with mild steel