Aren't you being a little harsh? Its not that bad an idea, even if it has been said before. Maybe it should be reconsidered. Anyway..
I'm not sure if it should be quite that strong, that would give Trunks a one hit capability that would make him almost unbeatable. But, it might be an idea to have the sword as a weapon that could be enfused with his ki and made a lot more powerful. It would cost something like 10000 ki per second of use and boost the attack power by X100 or X1000.
So, when unenfused it would be slightly stronger than melee and when enfused it would be incredibly stronger. But the catch is if over used, the blade shatters, enfused or not, and is lost until you die ten or five times more. When that happens the blade comes back.
I'd do this because, though Trunks chars need some kind of advantage, that sort of powerful weapon could give them too much of an advantage. This way they can fight back against the Vegeta and Goku players, but not beat everyone in sight. How about that?