I just think Mirrorwatch would be more interesting if it was a non-canon story where Lena's chronal accelerator malfunctions and puts them in a different timeline. (Though I hate the idea of multiple universes, timelines, and all that, but again, it's not like it would be canon.)
Obviously, we don't know if there will be a Mirrorwatch comic or anything, but as of right now, it sounds like our favorite characters are just, well, mirrored. There's nothing interesting going on as far as character dynamics go.
Imagine a short comic where Lena finds herself at Watchpoint: Gibraltar, except all her friends are now villains, from the Commander Morrison to even Winston. Talon Winston and Talon Mercy would want to capture Tracer to experiment on them, but Overwatch comes in to save the day. Then, Lena has to work with them (even Widowmaker!) to steal technology from the Talon-ified Watchpoint: Gibraltar that could get her back home.
Then, after the event ends, it's revealed in a second VERY short comic that it was all just a bad dream. Lena wakes up in a panic beside Emily, and Emily comforts her as they both drift back to sleep. The end.
Am I saying all this because I'm salty over the existence of Talon Tracer and the fact that Soldier: 76 and the Reaper guy were seemingly ignored? Well, yeah, that's part of it, but hear me out--
A little Liassidy hc I have is that Cole and Mina's relationship was fairly secret. The only person knowing being Jack because he was close with Liao and I think she would have had a harder time hiding her relationship with Cole then Cole did.
So here's a little story post with that in mind, along with some OG Blackwatch.
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*Angela, Cassidy, Amelie and Gerard are hanging out in an Overwatch base common area. Amelie and Gerard did a couple thing, Angela and Cole made fun of them, Amelie finds it amusing, Gerard is done with their shit*
Gerard: When are either of you going to stop making my life a living hell?
Angela, smugly: Never.
Amelie: Gerard you need to calm down, we can make fun of them when they start dating.
Gerard: HA, like anyone would want to fate either of them, they'd need to be delusional!
Cassidy: I don't know, there seems to be something between Angela and Genji recently.
Angela: *lightly smacks his shoulder* Like you would know if something was happening between me and Genji. You haven't dated anyone since Deadlock.
Cassidy: Hehe, that's what you think.
*Angela and Gerard go quiet as Amelie leans back, ready to watch this mess unfold.*
Angela: Cole what do you mean by that?
Cassidy: I meant what I said.
Gerard: No no, have you dated someone without us knowing? Are you dating someone now?! Who?! What do you mean by "that's what you think"?!
Cassidy: I mean that's what you think.
Gerard: oh my god- Reyes, Amari!
Ana and Gabe: *just walking into the room* hum?
Gerard: Who is Cole dating.
Ana: Cole's dating someone?
Reyes: *shocked* What do you mean Cole's dating someone?!
Amelie: They don't know if Cole's dating someone, they're trying to figure it out.
Cole: Welp I gotta get some training in, talk to y'all later.
Angela: What- NO! You don't get to run away from this! Answer our questions!!
Cole: *calling behind him as he's exciting the room* Sorry in another room! Can't hear you!
--Years Later--
*Angela is recounting the story to Fareeha and Genji in the dining area while Cassidy is helping cook dinner.*
Angela: And we never did figure out who Cassidy was dating back then.
Genji: I wish I could say I knew but I never asked him about that stuff back then.
Fareeha: Same here.
Genji: Also be fair I doubt either of us would have wanted to hear about his romance escapades back then either.
Fareeha: Speak for yourself, I loved hearing the shit Cole and Ashe got up.
Jack: *walking into the room and seeing the three of them trying to figure something out* What are you three talking about.
Fareeha: We're trying to figure out who Cole was dating back in Blackwatch.
Jack: ...When was this?
Angela: After I stopped working with them.
Jack: Oh, he was dating Mina.
Genji, Fareeha and Angela: *stunned silence*
Genji and Fareeha: WHAT?!
Angela: Cole you were dating Dr. Liao?!
Cole: *yelling from the kitchen* Morrison you bitch!