The way I see it, is you have 2 methods:

1) Like Arma 3 life, Battle Royale, TacBaf, etc. it starts with 1 server running the mission 24/7 (with planned restarts, yadda yadda).

The only people you would be working with, who have an invested interest in working with you is: Someone who maintains the server, someone who maintains the website associated with the mods, someone who maintains the publicity of the mod, and someone who maintains the mod/mission itself. One person can play multiple roles, but you get the idea.

This would be your core team, and anyone one else is more or less extra fluff within the community (be it testers/server mods and admins, donators and other regular players). You basically have a community who plays your mission/mods and they pretty much stick to that. (like TacBaf or the Arma 3 Life group)

2) Like Altis Life, wasteland, Inavde and Annex, ect. You promote the hell out of your mission, have people throw it on their public servers, and have a central place people can provide feedback to you (like a forum, or thread on the BI forums).

You wouldn't necessarily be working with people as a team, but you would be sifting through tonnes of feedback by server operators and players alike. And if it was popular enough, you'd have more and more servers pop up ran by various people that are out of your control, running their own edits, or preferred versions of the map.

So it boils down to how you want your mission to be distributed.

Controlled Or Uncontrolled, and if anything I said seems unclear or you want me to expand on some stuff, ask away.

But there is one thing that should be said. You can't force it's popularity, and you have a very high chance it will not catch on, no matter how many hours of work you put into it. Welcome to every up-and-coming game designers life.