At the moment, the game looks like it will be fun as long as you haven't played all mission. There haven't been any information on what to do after the story missions. Offcourse you can do every single side mission and try to find all supplys. But I personaly don't like searching for supplys that much. My Suggestion want's to adress this issue.
I suggest to add some sort of 'map editor'. I don't know how hard this is to implement in the current engine, but there are different 'feature levels' it could possibly have.
On the basic level, the community should be able to create theire own mission. Place patols(incl. pathing), guards, mgs, vehicle patrols, mission objective(s) and create a own mission on a place/city that's already on the map. So no placing of cover, guard towers or even buildings. Most likely a more complicated way for the devs would be to allow players to place small covers and guard towers. Now where it get's even more intresting is, when we would be able to place own buildings, maybe even change tarrain and create our own untakable stealth mission. As I can't tell what effort it takes on the game's engine there's one thing i really want to see: Global Leaderboards(seperated by stealth/loud and SP/COOP) for each story mission and each community created mission, if this feature might find it's way into the game. I hope you like this idea and can see how this gives the game an unlimited endgame!
TL;DR: Community should be able to create own missions and meassure their skills on a leaderboard!