As the title said, is it possible to change from the original server to player to player to player connection, just like those other games, e.g. warframe. I think that could really be a good way to solve the geographic lagging problem as I believe it won't require the hosting player's computer to be extremely powerful. This can also reduce the cost of servers cuz GH can just host the haven and guild only. Maybe the dev can give a try on PvE and then on PVP? Will these things be possible?
It isn't a realistic possibility at this point (as it would require recoding most of the game, to start with), but it's a lovely thought that you've had. There are also very few if any peer to peer packages available to the public written in Java that I've been able to find.