https://www.reddit.com/r/overwatch2/comments/1k6pnm0/i_think_that_if_archives_returns_this_will_happen/
Overwatch Stadium has 17 heroes. 4/17 of the heroes are Reaper, Genji, McCree/Cassidy and Moira. These 4 are the Overwatch Retribution Archives mission hero select characters for the story version of the mission. So if you combine the Archives mission with their Stadium item shops and ability enhancement selections you pretty much have a story version of Retribution “Hero Mission” variant.
Hero missions were going to be “level up your heroes the way you want, play different ways, use different strategies for x boss and y scenario etc” but with ALL heroes. Why not start with story mission heroes and then implement it in retribution all heroes once everyone in stadium has their “talents”. Or in other words, once all heroes in the roster can be played in Stadium.
Then there’s the fact that each Archives mission has an extra area added. They could be used to make the mission longer or as “quest” areas to get extra money or talents to finish the final boss area more easily or something BUT at your own risk since you have to choose how many waves to go through cos if you lose there you lose the mission but if you exit in time before another wave starts you can clear the mission more easily.