Although hollow in the buttstock, I'm pretty sure the kit would be able to withstand take a hit from a paintball under normal conditions. I do have to say, though, that I've never experienced getting hit by a paintball or even seen first hand a paintball hitting anything. I know there are speed limits to them in competition but for souped up paintball guns, I'm not totally sure.
The only area I would think a paintball could break anything are the webbed areas of the barrel shroud. (The plastic parts between the holes.) The sights are a little flimsy and might break off if it's going to be handle roughly but they can be removed.