Hello
Here are a few ideas for new event:
1/ Monster hunter : Some bosses (new or instance or wb depending on your choice) pop randomly on different map (maybe one map per region). Players have to find them and kill them. It sounds like the hunt for magical eggs during Eastern festival, but in outdoor environment. Maybe with another concept : By killing the boss, you get one item you have to bring back to a NPC for rewards (at your discretion ;))
2/ Defend fortress : Years ago, such an event was implemented in the legacy game. Players had to defend the dwarf fortress in the redhill mountains against hordes of monsters. It was a world event involving all of the volunteer of the server.
Of course, due to the gap between VHL/End game and Low Level/Mid Level players, it has to be adjusted, maybe using an alternate map such as castle ground : Such a way, their might be groups of players in accordance with their lvl + gear. Hordes of monster objective might be to destroy the castle throne, while players'one should be to prevent it.
Regards,