alignment issue with rear wheels, no adjustment, frozen bolt

The rear tires were ruined due the lack of rear tire alignment capability, they cupped badly and had to be replaced prematurely. The rear wheels were both out of camber and toe specification. The only adjustment available when automobile is new is a small cammed bolt on a lower control arm. This bolt is not stainless nor is bushing material a compatible metal so they quickly rust or fuse together which prevents alignment shop from being able to adjust the toe. There is no camber adjustment at all, so when springs, struts and other bushing settle the car will soon be beyond the +/- 1* specification. Dealer and alignment shop both felt only solution was to cut out arm and replace with a new OEM arm which would eventually lead to same failure mechanism. Alternate solution was aftermarket suspension kits that would provide both toe and camber adjustment