When I first got into ArmA (a few months back) I had a similar idea, got some missions made, worked on some scripting, built the first set of missions, but it never ended up going anywhere, below is link to a doc showing a rough idea as to how the story progressed to the end of the first series, but as the first series never happened I couldnt find time to do anything further, feel free to grab any inspiration from the doc.

Story Missions

I even set up a dedicated Discord Server to share ideas and hold informationand links on - But again could only get 1 guy involved and he is now building Malden Life stuff - More info found in the discord channels

Story Mission - Discord

Interested to see how you get on, best of luck.