As others have said, SCCA does not allow any kind of modifications on control arms. PCA and NASA are more (not surprising) accomodating. Reinforcing the control arms can lead to failures in other places if the arms become too rigid.

In your case, with the steel arms, you are in much better shape than those with later aluminum units. Start with OEM parts or at least German made units. Inspect the arms for stress cracks, especially around welds, before every event. Change the ball joints every 5 or so events. Change the arms every 15-20 events and you'll be fine. I've been running on reinforced steel control arms (ITE, retrofitted from aluminum) for over three seasons with zero issues.