IIRC, Psions still have the old 'Sorcerer Subguilds' and don't get to pick higher-karma subguilds or extended subguilds or whatever. I imagine that'll be updated at some point to just allow them to pick a different ext. subguild, or maybe they'll get an overhaul like the Sorcs and get split up. Could be wrong! Maybe this changed when Sorcs changed.
If I also remember correctly, Staff said that you can't combine like...Well actually now i'm confused because all the 'karma' options are subguilds now, and races I suppose. But I think you can't combine a karma race with a karma subguild that's higher than 8? I dunno. I think right before the "Magick Subguild" move, you weren't allowed to combine say, a Krathi with an Extended Subguild. You could pick a karma guild / regular subguild, or a regular guild / karma subguild.
I think typically Staff unlocks a race or guild or subguild option you don't have for a special application, and it gets removed automatically when that PC dies. If you gain Karma from that role, it stays unlocked (if it is in that karma category). I've accidentally had stuff 'stick' through, even when I didn't have the karma for it, and I notified Staff for them to take it back off.
Mul Sorcerer would be so OP it hurts. But, I do think if the CGP system were eventually unlocked, it'd be cool if 8 was no longer the maximum karma. Make it 15.