I would very much support a sword in the heavy weapon slot to gain more variety. If the sword was exotic rarity and hard to get, it would leave room for it to be a strong weapon. Personally I think it should be different from the sword of crota, which takes away your super and melee abilities. A simple lunging melee weapon in the heavy slot that can be used in conjunction with a classes abilities would be great. The gunslinger could still throw a knife between slashes and the blade dancer would have a small blink slash, warlocks would get their buffs, and titans the same case.