I've seen 3 w126s with rotted control arms so far in 3 months. Two at an indy and yours. The one at the indy near me was so bad it was horrifying. I would love to have taken pictures of it now lol. My advice is the same as pawo's. Weld it up, POR15 it and get a few more years and in the mean time pickup a spare until rust is prevalent again.