I'm still not sold on Top/Bottom / Dom / Sub should be listed, TBH, I don't like how people stereotype "Dominant Top" or "Submissive Bottom", IMO it's too cliché and over-used. That's why "Small on Top" is high on my list (but it kinda goes to the opposite extreme XD)
But I like your idea of an "External documents" that list all the characters and their positions (or at least some hints). So people want can look into, others don't need to worry about being spoiled. IIRC, most Japanese games have this feature. And this will be more useful for WIPs and their backers.
There are few games even have a brief "Official walk-through" (For free, not those sell for more than the game itself), goes into more details about things you might wonder.