Regarding the weapon specifically, there are some tweaks I'm thinking about.
Two charges of three damage, even at the cost of life, is crazy good. The effect is probably better than stuff like
Staggershock for removing creatures because it leaves behind a resource you can cash in at any time, one that your opponent will be hard-pressed to play around. Just like Fiery War Axe in Hearthstone, their two-mana removal kills your turn two AND turn three; you have no choice but to offer up a sacrificial lamb and go behind on board.
Maybe an echo cost would be good here? It makes the opponent's decision in the face of the remaining charge more interesting - do I trot out a target and tie up his mana, or do I just land drop and durdle and see if he pays to keep the charge? Some hands will be able to out-scale the three damage, or have plays they can make in response to the activation once they have more lands in play, so for them passing turn three will be a risky but viable option.
Another idea: If it only targets attacking or blocking creatures, then the opponent gets to decide when you have opportunities to use the charges, and it becomes much more vulnerable to artifact removal. It becomes more about getting attacks through with the threat of chopping down blockers assigned to trade.
I'm not sure it's still playable or an attractive design with that change, but it does feel less like a trespass into not-green design space.