Context
Geoff talking about Mercy (which was nice to see)
Ok, so, Geoff talked about the possibility of putting an extra effect on Mercy’s damage boost.
They may or may not have something in mind, and the forums shouldn’t go off and say “they are going to change her” quite yet.
But… there is a REALLY interesting idea on what they could do with her based on it.
Give damage boost aim assist. I know, it sounds CRAZY at the start, but, there is a lot of goodness this has as an idea. It gives her identity, more impact, reduces toxicity, and the game already supports it.
Identity
First of all, it cements Mercy as the DPS’s support, which, gives her more of an identity in the game, AND also it gives her a Niche (not as in, Oh that character isn’t garbage, they are just Niche - which is short hand for Garbage, but, an ACTUAL real honest to god niche)
Impact
It makes damage boost more consistent, but doesn’t break the damage thresholds which the heroes are balanced around.
She has had a problem for a long time which means people don’t feel like she has impact in the game. Her ability to influence how combat goes has been somewhat lacking for some time now.
Toxicity
One of the things which Mercy players HAVE to be good at is assessing how good their DPS are, after all, you have a huge opportunity cost to using damage boost. If they miss their shots, you have been 5v6ing because Mercy is literally doing nothing.
So, it causes a problem. If your DPS can’t hit their shots, what do you do?
Inform the team so they can support them more? it just… causes toxicity problems.
But with this, you can ACTUALLY do something about it. Since you can literally heal bad aim.
It is also VERY much in Mercy base game play, since, you are about enabling team members to shine.
It also leads to funny interactions.
It is actually solving the problem in your team, rather than blaming people. You don’t even have to let them know that is WHY you are doing it. After all, if they are hitting their shots, you want to boost their damage anyway 
Development
As for coding, Aim assist already exists in the game, the hit check against the hit boxes (well, sphereoids in overwatch) already has the code in it. So it isn’t that much developer overhead to put it in. It is also in the most well tested part of the codebase.
I KNOW it sounds crazy, but from a systems point of view it works perfectly, and it solves a LOT more issues than it creates.
TL;DR: Mercy having the ability to heal bad aim sounds like a joke, but it is a really good idea.