Great to have you on board, I'll add your name, thanks!
And yes, that would be an awesome exercise around the themes you indicated. Adult doesn't necessarily mean raarrrhh errrotica or brrrr horroooooorrrr/gooore, you know?
I wouldn't say there's any specific requirement about using content that's already appeared elsewhere or new, although I would personally prefer new content (anyone can chime in on this, though). My own story will appear both here and on my website, for example, and likely roughly at the same time. If we can get this started, you will have to submit your work by 15 October, I hope that gives you enough time for your SFW comic to stabilize. And then again, once you submit your comic, you may ask for it to be published further down in time, if needs be.