Some sniper rifles in real life are pretty trash for anything but sniping but there are several with a semi-automatic setting which can be used effectively without the scope should a situation call for it. Long arms with the "sniping" special property would take care of most concerns pretty solid.
I think you could have long arms that are unwieldy and "sniping" that represent some of the higher caliber, more damaging sniper rifles. The general damage curve of weapons that most all weapons follow doesn't really allow for that though. They would have to break the bell curve everything is based on to make such a weapon. Mean while, sniper rifles in star finder are fairly useless outside of a small handful of specialized and unlikely situations.