So.. you're a sorcerer with the ability to possess things, and you get your bloodline spells and such..
You get up to level 19, and get a pretty cool spell - Divided Mind, letting you cast two spells a round up to 5th level like you've got a free quicken spell going. You can make two will saves, two int checks..
Only problem. You hit level 20. You're now immune to Mind-affecting effects, which divided mind is, and you lose access to 2/9 bloodline spells
Am I reading that right?
By pure RAW? Yep. You don't have a way to get rid of immunities, or really go through them, so you aren't able to use the spell once you hit level 20.
Obviously, if you feel this is unintended, house rules are a wonder, and I could see most GMs agreeing that the level 20 ability should only affect hostile mind-affecting effects.
It does feel pretty unpleasant to get a cool spell but have to give it up the level afterwards.