By the title, you know what this is about.  Be able to customize:

• Conditions required for the particular quest to trigger (so any combination of Empire/Kingdom/race/faction etc/Sovereign/Champion/regular unit/city/building/map site/turn number/diplomacy state/item etc. - basically any criteria that can be checked for in a map) including stat requirements of particular types of unit/s for the quest and also percentage chance a quest will appear if the conditions are met;
• Text for quest (and optionally, pictures and sounds), based on criteria;
• Requirements for completing quest successfully (eg. particular unit (one or more than one) must complete quest, time limit for quest (from the turn when quest is received or a specific number of turns in the map);
• Steps for completing quest successfully if it's a multi-step quest;
• Possible things that happen if you fail the quest.  AND
• Any other details that would be relevant to creating a custom quest?

What do other people think, including Frogboy?  I think it would be great if custom quests could be made, and be data-driven like a lot of the other facets of the way Elemental works.  And I forsee you could make some very cool RPG maps with a powerful, intuitive and comprehensive way of making custom Quests. 

Best regards,
Steven.