First to the OP, no. You cannot run dual AL. I just have been down this road in the last 3 weeks on the crew cab. The stud on the front of the truck with a single AL is not long enough!! lol So out come the studs this past weekend....
For the rear, with a single steel and a AL, it JUST works. Like by two threads. LOL Each of my aluminum wheels are .75" thick. The steels are half that. So picture 4 steel wheels trying to fit onto those studs.....
As for the powder coating: Powder should NOT peel even if chipped. If it does, the surface was not prepped right. I work closely with powder coating as part of my job so I can tell you that of all the stuff I have done, none of it peeled. Hell when I have to get it back off, even sandblasting it to get it off it doesn't peel!! lol I have to basically chisel it off with the sand.