So basically it sounds like the main issue with OP's idea is how after 60 seconds the user would be teleported into something that they didn't agree to be doing to begin with? The rest of the idea is sound considering we already have a system that allows players to invite other players to battles/teams and those who are asked to join get a popup. So it's not too far a stretch to have a group's leader and battle commander have a *on that creates a popup that invites players that would already be eligible to join a team to join a group battle/event such as Great Ninja War.

Now I also understand where the moderator is coming from. The inviting system we already have does not make a decision for the person invited if the invited person doesn't make a decision, which makes sense considering I wouldn't want to find myself doing something I didn't agree to already in the first place.

"... And how something that would possibly bring them some good rewards it's against their will? If they prefer to do treasure hunting to get some level 2 magatama instead of being able to receive some seal scrolls which by the way is a scarce resource it's not for me to decide, but that is the role of that pop-up, to decide who is afk and who is not interested."

Per my above points, the popup shouldn't really decide who's afk or not since that's not what people are expecting a popup asking if you want to join GNW or whatever to really be asking.

Perhaps an additional idea to the OP's idea might be to allow group members the option to auto-join GNW battles when they show up, maybe in a similar fashion to Sage World Battlefields.