@faraday The usual MUSH/MUX scheme is actually a fair bit like that, except that the original FCs are usually active PCs.
The very earliest Amber games were a lot like the early Vampire games, in that being Someone Special (a member of the royal family or an actual supernatural creature, respectively) was pretty restricted. More recently the style in both genres is to accommodate whoever wants to play whatever, although the last few generations of Amber games have also been pretty good about making characters who aren't royals be able to operate on a mostly equal plane with them, in case someone doesn't want to be part of this lunatic family.
Unfortunately, the early genre was heavily influenced by Erick Wujcik's vision of the book characters as people you Did Not Get To Beat (there's a particular notorious story about Morgenstern and a PC's magic dog), and so they tended to get a lot of stuff that other PCs simply did not get. That has softened some over time, so that, for instance, RtA's Benedict, Corwin, and Eric are actually beatable in swordfights by nonbook characters (something that was literally impossible on AmberMUSH), but even the most liberal game visions tend to place the book characters, or at least some of them, as special in ways that are difficult or impossible for others to equal.
I understand the reasoning behind this, because what's the point of having Benedict as a character at all if any random yobbo out of chargen can whup his ass? But I don't really like the effect it seems to have when those characters are PCs (see sentiments expressed by various people above).