There do not seem to be any limits to how high the Inquisitor's Psy Rating can climb, nor how many Psychic Powers, Ascended or otherwise, he can accumulate short of what XP expendatures permit via the Psyker's Gift Trait. Does this not mean he can eventually exceed a Primaris Psyker in power?

Yes. After all, look at Lottie; a.k.a. the Burning Princess. She's a rogue Alpha level with a Psy of 14. A Primaris can hit what, a 10; 6 for Psyker, and a +1 every even rank from 10 on? Remember; though, Elite Advances still have to be approved by the GM, even when built into the description of things. I would probably limit the purchase to no more than one Psy advance per rank; whether it be rating, or powers. But that's just me.

EDIT: Ooh, forgot. If you're particularly radical, your Primaris could hit a 12 with Sorcerer and Master Sorcerer...

-=Brother Praetus=-

Not to mention that the Inquisitor can take a +10 Willpower Transition package; ****. Looks like the path is obvious for making a totally pimped out Psyker. Assuming you could advance your Psy Rating at 1 per Ascended Rank, and took Sorcerer/Master Sorcerer, you'd wind up with a final Psy Rating of 16!

Yeah, potentially. And then push it for a maximum of what, 19-20; with a whole lot of interesting side effects to be had. Oh my God-Emperor! What a sickening thought.

-=Brother Praetus=-

Brother Praetus said:

Now where did I put that ancient D&D Immortals supplement? At Psy 16+ what the heck are you still doing crawling among the puny mortals? You should be busy kicking the old stuffy Imperial Saints in the Warp for their place on the Big E;s feet !