I forgot to respond to this.
I think with my idea, it would actually put a huge skill ceiling onto Mercy. It can be used in a multitude of ways whether that be as an engagement tool or a disengagement tool or a mid fight utility tool.
By making the lock on based on health makes it more challenging for the Mercy player to rez tanks and makes it a feat in order to do so. While Resurrecting squishies is much easier and safer.
If you take Ana for example you can use Nano defensively or offensively (I’ve had games in Masters where an Ana has nano’d me during a Rez in order to keep me alive, then I got a kill afterwards), same with Trans Beat and Coalescence so why does Mercy have to be different?
If Mercy loses sight of her teammates she won’t be able to Rez them, if she pre-Valkyrie’d then use an ultimate to take her out or be prepared for her to Rez and take action accordingly. The problem with Rez was it didn’t have a warning or any signs to react to it.
Therefore when she pushes Q she gets the “I will watch over you” voiceline which is the cue to the enemy Mercy has ulted, then the second Q press would be her “Heroes Never Die!” voiceline.
5 Man Rez wasn’t oppressive or powerful that’s why she was in D/F tier. The problem was it was annoying to play against because you didn’t know where it was coming from or had any way of predicting it was going to happen.
We could add a 0.8 second cast time to the second Q press to make it 100% counterable too but feel much more rewarding if you pull it off? Honestly i’ve stuck with this idea for a year and it sounds much more fair to play against than old rez it would feel much more engaging than old rez and it would be much more fun to play with then current Mercy.