I probably wont participate too much in it if they had it but if they did I'm sure their will be players playing large-scale PvP

But imo this shouldn't be their priority should be lower to the list of things they need to fix, content to add.
Do it MAG FFXIV version... Gridania VS Limsa, you got different parties (squads) with squad leaders communicating with other leaders getting information from commander on current status of war.

Do it so you can take over like a fortress or something, and at times have the beastmen or the empire? (dunno English name for Teikoku 帝国) come in to try and take over making it PvE against whatever country owning vs Beastmen or Empire.