First off, I love it more than most stuff in this book. Seems like this class and Discipline is as close as PF comes to a Scanner.
Survival: I love it. Even fits with how the guy in the above clip starts as a hobo.
Mental Placidity: I'm a big fan of immediate actions. One that buffs your will against an incoming mental attack and can provide a buff to fellow party members affected is gravy.
Sleep bonus spell: Sure, sounds good.
Detect Thoughts bonus spell: Errrrn. This is where I'm raising an eyebrow. Every other Discipline gets a second level spell at four, but not Tranquility.
Detect Thoughts is a natch first level spell for a Scanner. Add to this the fact that the only Psychic Spell offered at first is a mind thrust, which is a divination that offers HP damage and a Will save, and is also extremely Scannerific . Spell Focus: Divination seem like a good first level feat, maybe? Considering that Detect Thoughts looks like the only other divination with a Will save at first level, and the two work extremely well together, flavor-wise.
Sure, you can use your fourth level free swap to change it, but that means that your so-called second level bonus spell just became Your Choice of first level spell. You get two of those when you build your character and one at level three.
In another thread I suggested Calm Emotions, but I see that the Discipline gets that as a free SLA at 5th anyway, so may I suggest Silence? What's more tranquil?
Hypnotic Pattern would also fit the theme.
Good suggestions on replacing detect thoughts! I think you're right. These spell lists will also change a fair amount once we add in a bunch of new spells, so it's possible we'll write a new spell to fit that slot. :)
Is it PFS legal to substitute a second level spell? I'll try and keep it thematically appropriate.