Unfortunately, Blackguard sounds too much like its derivative 'blaggard', which sounds a bit silly in modern English speech.
'Pariah' fitted the ex-Jedi idea well but workms less well now I am moving away from that as the default so I am considering the new name.
I wish Venger (classic D&D Anti-Paladin) was in wider use...
As for Xavier- the PB classes will be mechanically identical. Still, I am generally sympathetic to character changes if it is not too absurd and repeated.