Explosive headshot is a must, just going to yoink that from TF2’s ACTUAL FUNCTIONING PVE!
I think there was an April fools or something where her ult could reveal weak spots, which were secondary crit spots. Doing that on a boss with like a 5X damage multiplier would be amazing.
Bouncing bullet too, like all enemies caught within a Venom Mine will just keep bouncing bullets between their heads until they’re all dead.
Widowmaker could maybe create reusable zip-lines with her grapple instead, which her teammates could also use.
Even something like a faster charging scope would be good.
And maybe replace her primary fire, y’know, Widow: 76. Maybe give it like a hip-fire sniper rifle?
Missiles.
They showed it off in one of the PvE showcases (inconsolable weeping), and it also came back for an event once. Instead of using her healing or damage boost beams, Mercy just shoots missiles that still heal and boost allies in range, but also just do damage.
Mercy could fly faster and further, and also crash into enemies to damage them.
Give her wings a flash-bang that blinds enemies and forces them to shoot wildly (they could also shoot and damage each other in the Feb 2021 Blizzconline thing).
Or maybe if healing missiles aren’t your thing, maybe the healing beams themselves also cause enemies to take damage if they pass through them. This basically creates a spiderweb of death and lasers during Valkyrie.
And I’ll do you one better than mass rez; rez aura. During Valkyrie, or maybe rez, IDK, Mercy gets a visible ring around herself and any allies that die inside the ring during the ability’s duration will be instantly revived. The ability will last a few seconds, so as long as Mercy doesn’t die and you stay inside the aura, just go ahead and melee a boss to death, there won’t be any consequences.