Here's an idea (might be a bad one but I like it)
A vore mode.
The story would also be a little different, instead of the decay god becoming envious- the life god becomes prideful and attempts to end decay and death.
Knowing that this would break the cycle and possibly destroy the world, they (I don't know the decay god's gender) pleads with a human (our protagonist) to take a small amount of their power (consume some object, maybe a corrupt seed) and then go out, collect more power and intervene to prevent the destruction of the world. Beings that have been infused with such an amount of life power magically mutate and become demons, eternally living beings that can only be truly stopped with the decay god's power. (Literally just the normal plot and game play, but backwards.)
The belly bash power would be replaced with the "Swallow" power, (if it kills an enemy then the Power Bar gains a large boost from the fight. And the characters belly swells up) So just that, some voice lines, and some (or maybe a lot) of dialogue would need to be changed. Also birth could possibly be replaced with "regurgitate" to produce another corrupt seed when the bar is full, these "living" things- brimming with un-life- would be used in place of life seeds.
I may not know how to make these kinds of games, but I'm sure I can learn to edit text, so if I need to volunteer to take on that grueling task to make this a reality, I will.