Every oil change inspect control arms, cross members, and subframe. I remove rust, prime, and paint. Think the metal or coating is inferior we purchased Dolores in October 2016 with 6 miles and the control arms and cross members were already full of surface rust. When Dolores was picked she was just delivered to the dealer.
Will this become a safety issue on the Mirage? Time will tell. If you DIY or good mechanic ask them to inspect bi-annual. If you DIY check the top of the subframe it will remain moist and hold gunk on occasion.