I wasn't going to participate, but then I kind of got the picture from the latest Roguelike Radio episode that if you are a Real Man (or a Real Woman) you can still make a 7DRL even if you had plans to live a life otherwise. So I guess I'll be doing this, announcement on rgrd tomorrow and all.
I was thinking of a roguelike that takes the Paradox Mage class concept from TOME4 and supercharges it. You can time travel into the past - maybe a few dozen turns at most (I don't know yet how much memory it will take to store the previous game states the way I intend to) and change past events. AI actors will respond to you in the past, but previous versions of yourself will be completely oblivious to your existence. Causing changes in the past will increase your Paradox resource, and the more you've changed the past from the original timeline, the more Paradox you will build up. Just like in TOME, a higher Paradox powers up your spells and strange powers but also makes gameplay more dangerous and chaotic, and it takes concentration over time to reduce your Paradox. I have a weird science fiction explanation for all this planned out, too.