a) The Marquis de Carabas, having realised he isn't immortal and may in fact be dying, shows up at Hogwarts to pick an apprentice from Harry's year (who have just finished), so he'll have someone to take over from him in the realm of scheming and general bastardry. For reasons I haven't worked out yet, he chooses Dean. They may at some point end up shagging, since this is apparently what the characters want to do - I've just got to figure out how to get them to that point.
b) Draco and Harry are lovers, but Draco (who is a Death Eater) leaves for both their good, making one final request - that should Harry defeat him without killing him in the process, he's to then kill him quick and clean rather than turn him over to the Dementors. Several months later, they do meet on the battlefield, Draco is defeated and Harry keeps his promise. That one's probably a (rather depressing) completed cookie, rather than a full-length fic.
So now I have to write them, instead of the hundred and one other things I should be doing. Great.
Incidentally, feedback on the value of these ideas, how they might best be made to work, etc, would be very welcome.