Regarding possible equipment damage:
I've done scrape bench presses and scrape overhead presses, and if the bar used has very poor knurling (like a lot of bars in regular gyms), the risk of damage to the bar or the rack is minimal. If, however, it's a good bar with proper knurling it should NEVER be used for scrape movements, unless you're willing to replace it. So in my old gym I would use the crappy "regular" bars for scrape movements, but never the good Pendlay bar.
Regarding scrape squats as assistance:
Not sure what Jim's stance on assistance work is, but ask yourself this - is the scrape squat the BEST exercise to address the SPECIFIC weaknesses that YOU have?