This would be the worst possible idea ever shown in this forum.
Seriously, a cross server gnw would mix together both the bad sides of cross server matsuri and cross server sage world battlefield.
Since they can't modify any minimum thing regarding the scripting side of the game the result would be *ways 3 rounds gnw on saturday whose only result in comparison with now would be to reduce the number of good gnw packs delivered. This would induce people in joining the strongest group of the server with the marvelous result that you would have more people among which the high tier rewards would be divided among and also less people to plunder since you can't plunder people in your group.
To do something like that you would need a massive revolution of how group activities work and an as big revolution as the other one about rewards for gnw.
So no, really, no, and please don't put in their head such horrible ideas, because they could become true.