I like the way you handle and mitigate it. I do have one other factor I put in which is a monetary cost. So with the Dragon Ascendent a class from the Draconomicon, the dragon can become a God but must eat their hoarde and it must be at least 100,000 gp. I do something similar, making the 100,000 gp cost go up at a 10 fold factor each additional Divine rank past 1 as a material component. I however make it so it must be something of that value or equivalent which can be highly subjective. It could be at the cost of the faith of a paladin, or the child of a father, the very forest a druid has sworn to protect, etc. Never a light decision. Something of such value as to create a total character overhaul.