You could try a living glossary chapter. What I mean is, have an entry for each major character based on their progression through the story marked as "Chapter X-XX" and then hidden in a spoiler. This way, if people can't wait for the big reveal, they can have their thirst for knowledge slacked. If they prefer to wait, they can. Bonus, even if a story goes on hiatus, people can look at this (if it's been planned enough in advance) so that they can figure out what's going on in each character's head.
It isn't the best solution, and it may not even be that great of an idea, but it would give readers what they want if/when they want it because it's just a glossary chapter full of spoilers.
It isn't the best solution, and it may not even be that great of an idea, but it would give readers what they want if/when they want it because it's just a glossary chapter full of spoilers.