This HAS to be fixed. Yes, shooters might be wildly inaccurate while it maneuvers, and yes they might fire off a RPG, causing all sorts of mayhem, but the first time someone tries to land on a rooftop and they get hozed down by someone in the top floor doorway, people are going to say it's broken.
In real life, soldiers would certainly be able to return fire from the rail, and there's no reason to make them unable to do so here. Perhaps incorporate the "raise" and "lower" weapon mechanics here as well? Makes sense to me.