I second this request.

There are a few technicalities that should be resolved when this is implemented.

First, if there are more players online then there are free slots in GNW, which players would be joined first? - Perhaps the ones with more power...

Second, what is preventing players that you "called" to auto-join to leave manually from GNW, leaving empty spaces? Should that option be disabled for those players? Also, if someone do exit from GNW would auto-join *on call them again, or it would choose someone else. One way to resolve which players would be called could be to implement another window with a list of all online players from group (that appears when "call" *on is clicked), and that there is a check *on for every player, so when you want to call them, only"checked" players would join.

One more thing, if someone is in a fight or in a ZENITH, doing instance, at home or something like that (when you cant call them to join team), could those player be interrupted by call, or it would be alloved for them to finish what they are doing now, and then auto-join after they are free again (although I think that would be bother to implement)? Maybe the best option here would be to be able to "call" only free players (except the ones in home bath perhaps).

This is a great idea, btw.

They said, Leader could call for his/her groupies IF they are not currently busy on what usually denies an invitation to join part of formation.
That was clear. Original Poster never said being intrusive if groupies are currently busy doing some home interface / arena / ST / Group Summon / team activities, or something else.
Don't be so extremist nor assume OP want to take away their Free Will. He/she just wants participation IF they are avaliable AND maybe away from keyboard.

I am not being a terrorist, I am simply asking for clarification on the nature of the desired request and suggestion.

Here is the issue with your current proposed suggestion. You propose a 60 second window where players are required to click away a popup or be teleported into great ninja war, but this assumes that they are not actively engaged in a system that would not be prohibited by this. Off the top of my head, they could be doing treasure maps and not find a fight in that time, or doing wanted missions and not find a fight in that time, or could be engaged in any number of things and just have stepped away from the computer for 60 seconds, which is a remarkably short time. They could even just be running between zones to do something, or be pausing between arena matches during that period and have gone to the restroom. Or they could be synthesizing equipment or magatamas and look away to have a conversation for 60 seconds, then turn back and find themselves literally in great ninja war. Etc.

My point stands that this system would be forcing players to do something potentially against their will. If these players wanted to do great ninja war they would most likely be doing great ninja war, I suspect. The reason I asked for clarification was so that the original poster could clarify how their proposed system would work around this problem and issue, which is a problem and issue, not to "be a terrorist." At present, this idea does not seem tenable unless you can propose a way around potentially making players upset about this.