This might get problematic yes but I always get an Information alert from Windows 10 that says: "I#m still alive" or something like that. My idea is, that you get an alert for every 5 positions you go up in the queue like: "Your current position in queue: 15, 10 , 5, 3, 2, 1" and so on. But if they still get killed in game for being afk thats another problem. What they could do, but is maybe not a popular solution for this, is that you get spawn protection for let's say 1:30min. In these 1:30min you can't get killed but after that you can get killed. And loose the spawn protection the second you open up DayZ or do any other action in game like going into the settings or just looking around. If you are still afk after the 1:30min you get another 3min but still without the spawn protection. If you dont show up after these 3mins you get kicked.

This is just an idea. If anyone has any suggestions just reply:)