I know @seaofserenity is gonna be all over this.
Regarding the server, you'd have to check with HR/Engineering/Clan XO and CO. I believe we tried an Arma 3 server and it ended up not working out. @SnazzyDuckling might be a good person to ask to start.
I've played Arma since it came out and love the mods mentioned above. Been in and run MILSIM groups. As I'm sure you know, takes a lot of work to set up the missions/meetings/scenario/mods/server/etc. I would start running more casual Zeus games to build up a group and then move toward being more organized.
Also worth a mention, ArmA is aging and I know a lot of guys are waiting for Hell Let Loose. The clan has essentially invested in that game and plans on being one of the first groups there when it starts. When it gets released, I imagine you will see your group dwindle a little bit.
Just my 2 cents. If you are willing to put in the work, don't see a reason not to try. Good luck!