I'm not sure that would be possible with Brucolac, unfortunately. If you would like for him to enter the game as older to better reflect his canonical age, that would be allowed, but he would not de-age at any point unless that was specifically his power.

For Sirius, that is a side-effect of the setting and switching from "magic" to "power", and we're sorry to hear that. We aren't saying that you would need to totally restrict them, but there would likely need to be limits in place lest he accidentally becomes too powerful with it, you know?

Seeing the "true selves" of characters is a tricky proposition considering the mystery of the game and any NPCs that the PCs might encounter. Not to say that it would be outright disallowed, but we would definitely need to talk something like that over first if you were willing to.