Well I went through the "other" payment options for purchasing energy and other packages; and I think you should add a few more payment options. For one, you should definately cooperate with Ultimate Game Card online credits. Ultimate Game Cards provide a wide variety of in-game credits and it is one of the most common ways I buy my in-game items, since Rixty Cards aren't as available for me.

Another service is Karma Koin. I've seen these flashy Karma Koin gift cards every where and I've looked on their website. They give 1% spend to charity or something like that. I think this is a good organization you should cooperate with in order to purchase in-game items.

If anyone else has suggestions for how to purchase Crystal Energy, etc. say so in the comments.