New World Boss!

I think a flying world boss would be a better idea.

Or to add to your idea, maybe its not one big boss, but 4 different bosses, one in each corner of the map, it would still take a combined effort to kill them all, because maybe once the first was down, you had a set amount of time to get the others killed as well.

I think something like that would be a good idea to link to alliances, to make it so there was a rather cool benefit to becoming allies.


And back to My idea.

I think a flying world boss would be kool, But not one that's constantly moving unless there was a special tracking system/quest that allowed a team to follow and find it.

It could stay in one general area per day, and there would be a quest chain with it, in which npcs asked for favors in return for tips of its whereabouts leading to a final npc that knew exactly the area it was in.
It could be killed via the quest chain, which would give extra rewards for the extra time needed. Or it could be killed on site, which would give the regular world boss drops.