If we are looking forward to more large scale events involving high player counts, I suggest taking a look of successful events led by other communities. For example, I've gotten the opportunity to participated in a few FNF events which were pretty successful with little issues in performance. For those who are not familiar: As the name implies, it happens every Friday Night where different tactical ARMA 3 communities muster their own members to brawl it out in large scale TVTs. I've attended it twice and from my experience, it was a surprising smooth experience, averaging about 80-100 players every time.
"Friday Night Fights is a massive weekly event hosted by Arma 3's Phalanx. It began being hosted by another group called Bravo Company with the objective to bring multiple outfits together in a large but friendly PvP competition. The event regularly gathers 80-120 players."
More info: http://phalanxgroup.net/forum/viewtopic.php?f=1&p=2
What I think we can incorporate from this experience?
-They have 4 missions each spanning strictly 60 minutes with a 15 minute JIP time limit, locking the server after that to prevent performance and balance issues.
-Opening up for other communities to participate had several benefits : 1) Everyone was on their best not to show SHAMEFUR DISPRAY on the organizations they represented which limited trolls 2) Communities from different parts (AUS, BRAZIL, and RUSSIA) pulled some unique squad tactics and overall strategies that were refreshing to see. 3) Meeting new people is always fun.
-They kept their missions bare boned with no AI, no objects and permitting only the following mods: CBA, TFAR (We can change to ACRE ) ACE, RHS, and CUP Terrains/Map(Optional for UO) to make it easily accessible for everyone.