Wars declarations are exploited in Darkfall (such as killing crafters in NPC cities). A war fee would make clan wars in progress. Clans would start fighting against opponent races instead of killing their own people, to gain the war fee. This daily fee should be paid previously or as a deposit and the war should end when there is no more darkfall gold left to pay. Suggestion is to delay war declarations by 10 minutes to reduce possible exploits.
I'd rather to have a basis fee (may be 300
Darkfall Gold) and a fee based on the member count of the attacking clan (for instance, 50 DF Gold per member). There is no more necessity for the 24-hours cool-down via using this fee. Sieges against clans of the same faction would benefit, owing to the possibility to declare war to all clans of the other side. Another way to reduce the cool-down for war declarations to 20 minutes and to introduce a gradual escalation towards war (friendly -> neutral -20min -> wary - 20min -> war).
Have fun!