Can't think of a good name for these right now but here's the idea..

Similar to Guildhests in that these take place in existing field zones with some area boundaries so the cost of development is low, but these will be advanced challenges for endgame play with appropriate rewards.

Types of challenges may include seeing how long you can defend a settlement or cargo from increasingly difficult waves of enemies, or an arena type battle seeing how many enemies you can defeat in a fixed amount of time. Your score is displayed at the end, encouraging repeat plays, and rewards could be scalable based on performance, like bronze, silver and gold tiers.

These would take less time than doing a dungeon but reward some of the weekly capped allagan tomestones as an alternative to Lv60 dungeons and PvP since people want more variety to reaching their weekly caps.