Okay it's late, but I'll do my best to explain. This is something that should apply to all God Slayers in the rp. *is super tired*

You know how Dragon Slayers are able to consume another element and then use both elements for a temporary time that gives a power boost similar to Dragon Force (Example: Natsu (Lightning and Fire) Gajeel (Shadow and Iron)? I think God Slayers should also have that ability to eat another element so they can enter a duel elemental state as well. It make sense both of these slaying magics have both mages consuming elements and to me it doesn't make much sense why a God Slayer wouldn't be able to do that. 

As well as that perhaps God Slayers can also get something similar to Dragon Force. It would be their ultimate state that a God Slayer can reach for that temporary time if certain conditions are met in order to achieve it. What the conditions could be is probably like something that involves consuming substances with latent magical properties or absorbing something. 

I hope that I'm not sounding too much like a jerk.