I second this notion very strongly. I know that the intention of the Corruption mechanic from the respect of gameplay is to act as a means of "losing", at least in some respect, but considering how both CoC games give you new interactions, dialogue, abilities, scenes, ect it's clearly also suited to be the playstyle of some players. I am one of them, I like to go all the way with it because I really enjoy the dominating effect it has. Getting to go full demon mode definitely makes little sense under the story's base premise, so clearly more content would need to be added to suit demon players, but it would be an absolute dream for players like me. It could be a balance, high sexual/lust abilities, more corruption spreading, but with many anti-corruption factions and locations villanizing you or even rallying forces against you.
I'll admit, I'm into the idea of the power fantasy. Here's a little idea of what I had in mind:
You've gone so far, gotten so corrupted, and clearly were more focused on selfish sexual desires than actually saving the world. Kysarra or some other greater demon decides you'd be more valuable to them if you were given their power and the explicit goal of furthering their ends. You transform into a mightier version of yourself, keeping all of the changes your encounters have made to you and preventing you from ever reverting to your original form or lowering your corruption again. You gain power in nearly all categories, especially in the areas of sexual domination and dark magics. Every enemy you defeat becomes corrupted after you use them to fuel your never-ending lust. You gain more corrupted and demonic companions, amassing your own little harem of corrupted, lustful slaves. Those left who resist the demons in general send their forces after you, giving you large group encounters to really test your newfound power. With every battle won, more and more of them turn to the side of corruption, leaving trails of them mating and masturbating furiously in your wake. Your end goal is obvious: Plunge this world into endless, unending lust and corruption. Build and play with your collection of slaves, dominate their minds, eat their souls, and in general be to them what Kysarra was to you. Speaking of: Being a demon doesn't just mean you'll be dominating everything. There's still a whole hierarchy for you to climb, and you can be sure that those above you are going to do their best to make you submit to them and keep you in your place. Fight and dominate them, or submit and be their willing toy when you're not busy spreading corruption. Also, beware of up-and-coming demons and other corrupted entities looking to dominate you as well. Submit and watch them grow in strength as they use and abuse you, or keep them in their lowly place as the mighty demon you are. However you play it, the full power of demonic corruption is now in your hands.
Obviously all that stuff I wrote up there is just me dreaming up what it'd be like, but I think you get the idea. This stuff would be awesome. If it isn't included officially, maybe in a mod or something. Hell, I'd offer to write for it if possible, though I'm sure that probably requires some knowledge of the code or something to pull off, which I know nothing about. Either way, please, we really need this.
Pretty please with a cherry on top.