No, I will not write this, but maybe someone else out there can. I have stated on another Miraculous crossover story that I have fallen out of that fandom, and the Arrow fandom I'm not as active in either.
Adrien arrives for fencing match in Starling City
Stays with Queens
Goes out nightly to relieve stress/stops a number of small crimes
-Unintentionally drawing the attention of Team Arrow
-Chat gets called by LB to be careful and try not to get caught
"Gabriel is in Paris b/c of company"
-He's somewhere in Starling
-Still suspects Adrien is Chat Noir
Marinette gets invited by Gabriel to see/study American fashion
-Dropped off with Queens, surprising Adrien
-Still no Gabe…
Arrow comes across Chat Noir, stays back as Felicity does her magic
-Watches on camera as he skillfully takes on 4 armed robbers
-Takes note of catlike characteristics
Marinette watches her partner from her borrowed room
-Wishes to run free but knows better
An unknown attack the next night has everyone in danger Oliver, Dig gets Thea, Marinette, Adrien to a safer place (Felicity is already in Arrow Cave)
-Ends up taking them to the abandoned subway-where the undertaking device was located
-Commotion behind them runs them to a dead end
-Trapped in a tunnel scene
-Felicity struggles to get them out
-Adrien asks hypothetical question about destroying a wall-mumbles about his lady not killing him later
-Transforms: freezing Marinette
-Uses cataclysm on wall into an abandoned elevator shaft
-Others shocked by that power: Marinette continues to process
-Thea looks down as Chat sees an elevator at the bottom but a door above them.
-Oliver/Dig assumes it fell during the Undertaking (Chat explains how he can see that)
-Rumbling from above has everyone grabbing for support
-Thea slips and falls-Dig holds Oliver back from a stupid choice
-Chat prepares to dive after her
-Marinette does instead, causing Chat to cry out
-The three watch as a pink/red light appears
-Chat sees a familiar spotted yo-yo coming back
-Watches it fly past and wrap around a beam
-Ladybug with Thea arrive back up
-After helping Thea on solid ground Chat pulls LB into a hug, of which she gladly reciprocates
-Chat's ring beeps signaling a 3 minute mark-explains the down side of using an extreme power
-Chat remarks his comment on knowing each other as civilians
-Thea disrupts their banter
-Discusses on getting to the door
-Chat comments on lucky charm
-Doesn't work that way (Explains lucky charm)
-LB uses Chat's Staff and her yo-yo to swing them to the door
-Chat de-transforms into Adrien, LB meets Plagg
Eventually back to Arrow cave, shocking felicity with the kids and the kids find out who they are
-Thea is obviously pissed
-Marinette and Adrien just roll with it
-Felicity is shocked that they didn't know their identities
-Explains that they don't know Hawkmoth's and now Mayura's full capabilities when giving their victims powers
-Marinette is very unsure in de-transforming yet as she's so used to keeping secrets
-Plagg gives some harsh truths Marinette de-transforms, releasing Tikki who gets on her case about the reveal
-Felicity mentions how their secret lasted longer than Oliver's, earning a glare
So, is it Hawkmoth?
-Goal: Unknown
-Powers: creating fear/chaos; repeats past events that create fear increasing in power
-Akuma name: unknown
-Akuma location: Necklace Pendant
-Capabilities in pulling it off questioned
-Could use some help
Arrow helps with distraction as Chat prepares with LB
-LB wraps Akuma wile distracted, Arrow shoots off necklace, Chat cataclysm releasing akuma, LB purifies, miraculous cure.
Everyone returns home
-Gabriel orders Adrien and Marinette home away from the danger of Starling City
-Nathalie reveals that both Chat Noir and Ladybug did end up in Starling City after the arrival of Adrien and Marinette
-Close out of Chat on the window sill of the guest room he was in
I think I had this titled "A Secret for a Secret" was because the threat of Hawkmoth and Mayura isn't something that Team Arrow can really do anything much about as they aren't well versed in the workings of magic. Each team knows the others secret identities, but nothing goes farther than that. Also I had this plotted originally before Thea found out about her brother being Arrow. So...This is up for Adoption.