If the other gods refuse to accept Sirion's rule of not walking the earth bodily after they become lesser gods, and if they refuse to allow a metal that can kill the gods, is that a deal breaker for Sirion? Would you have Sirion leave and not be a part of this creation if he can't have these things?
Is there nothing else that Sirion would want for the world?
I understand he is the god of civilization which means the advancement of 'human'-kind (or sentient races as a whole, however he looks at it) and therefore wants to give those sentients the freedom to achieve the potential they have for growth and enlightenment without overt influence from the gods. I just think there has got to be a way to give Sirion something he wants that doesn't automatically bind or cause detriment to every other god even if they don't agree.
I like Sirion. He brings a needed portfolio to the world. I think he could be a good ally for Ubariya (of course, Ubariya thinks most of the other deities could be good allies under the right circumstances). Sirion, however, is probably the one deity that holds the most similar ethical and moral beliefs as her. What I'm saying is I don't want you to give up on Sirion just because none of us agree with you on this. Frankly Ubariya is afraid it might be necessary to take this step but she is also unwilling to limit herself in this way at this point in time.