As much as this would be nice, I'd have to say -1 for the following reasons.
We've tried grapple guns before this one not tested but they were abused and buggy.
Were they fun, yes, but I think it would take away server performance unfortunately, and if they could grab players I could also see the issue of abusing it that way.
Good idea, I just don't see them getting another chance... just like plantable/throwable RBC's.