The old perk for Monte Carlo was to work around with melee. It granted melee energy for damaging targets with this weapon as well as having a chance to fully restore it on kill. Not a bad perk for melee builds, but I feel like a lot more utility could easily be drawn out with this type of weapon. It could potentially be a really solid gun and what I want could possibly happen. Possible perk/idea: Damaging a target with this weapon restores some melee energy, while killing a target has a 35% chance to restore a melee charge. If you get a kill with this weapon, increase melee damage by 35% for 5 seconds. If you get a kill with melee while this weapon is equipped, increase the damage of this weapon by 35% (20% in crucible) for 5 seconds. (Possible bonus, grave robber) What this would do, is float the weapon around between firing and meleeing a target to keep the user in their face. It would reward super aggressive gameplay while supplying good buffs to keep the cycle going. It might not become some crazy pve exotic weapon, but I could definitely see it being fun, especially for the titans. I think some form of rework like this will come, maybe not with the same percentages, but something along those lines. If not, I think I'd genuinely be disappointed (not that my guess was wrong, but rather it escaped a potentially good rework like all autos) and would probably just ignore it like I did in d1. It's a fun weapon, but extremely niche especially with a lot of subclasses having a good form of ability regen, with melee almost always being the least useful.
I loved Monte Carlo in D1, combine it with synthoceps in D2 and it would be beastly! And I think Grave robber would be a good masterwork perk