Honestly. I’m against this idea. I’m all for special events, but clearing a mission if ONE player completes is, is too much. Logically it makes perfect sense that after clearing the mission it should not be available because you already defeated chickens, but it would be really chaotic in real life.
Also take a look at missions progression DURING EARLY ACCESS:
December 2018
10,000 total missions flown
Milestone achieved: 10,000 missions
March 2019
100,000 missions flown
Early Access version 15
May 2019
over 200,000 missions total
Early Access version 18
March 2020
650,000 missions in total
Early Access version 35 - #7 by InterAction_studios
We’re still in early access. Imagine what it would be when the game will be released (and also if it will hit popularity)
P.S
Copycat.