Black Crusade Psykers (Human) begin as "Unbound". Considering the Imperial "norm" of Sanctioning you may want to take a look at that and decide whether you will allow a Sworn Cadre Psyker to be Unbound. PC origin (such as Homeworld, if you're planning on using such things) or the back-story of a PC's life prior to induction into the Inquisition (a Player write-up) might allow this to go either way. However, Oblationisits are pretty picky when it comes to their secrecy; no one is introduced to their "inner circle" immediately, and they keep a close eye on all Acolytes to make sure they remain unsullied by Chaos enticements, taint, and Corruption. Acolytes who fail are executed, and the training process begins anew with fresh recruits. Like Xanthites, I'd imagine Oblationists would share the secrets of Sorcery with Sworn Acolytes (it's just another weapon in their arsenal) and this could allow for a psyker to "break the bonds" of his/her Sanctioning, thus allowing the use of various Paths To Power (Blasphemous Incantation, Corpus Conversion, etc). I'd be inclined to disallow Bound Psykers the use of these Paths To Power.
Chaos Space Marine Sorcerers (Astartes Librarian infiltraitors) are "Bound", and I think this represents both their resistance to the corrupting effects of the Warp and strict mental training and conditioning. But this does bring up another interesting question: If someone wanted to play a CSM Sorcerer (Astartes Librarian) would you allow for its inclusion? I read a short story by Chris Pramas about a White Scar who tried (and failed at) infiltrating the Red Corsairs with the intent of assassinating Huron Blackheart. A Tactical, Assault, or Devastator infiltrating the Screaming Vortex is not a difficult concept to stretch: he's a volunteer, he knows the risks inherent in the (extended) Mission, and he's hard as nails, now he just has to act like a disenfranchised bastard, maybe trading Ancient Warrior for Deceive? I don't think an Apothecary would be allowed to volunteer (just my opinion). Now a Librarian…could perhaps be a Lexicanum fresh out of Scout training? New to his power armour (if even), his powers only (relatively) recently recognised and his training within the Librarium having only just begun would be a good way to indicate his lesser (current) abilities, the mechanic being that he is Bound but suffers the effects of Corruption to a lesser degree than would un-augmented Humans (per the BC rules regarding CSM Corruption Thresholds being less frequent). Off the top of my head, I can't think of a validation allowing such a PC to use the Blasphemous Incantation, Profane Symbols, and Sacrifice Paths To Power. Corpus Conversion and Unnatural Willpower would be usable. However, I don't see any Space Marine taking the Oath of Oblation (maybe a Relictor?), nor do I see an Oblationist Inquisitor allowing Space Marines into his inner circle…it may be that, due to the radicalism of Oblationism, Space Marine PCs may have to (initially) be excluded after all? More to consider. Using a Relictor…or one of those sketchy Blood Ravens…might allow you to get around some of this.
Relictors would be a perfect fit for non-psychic "CSM" PCs, but does the Player want to play one? Would an Oblationist Inquisitor trust the Relictors? I see Relictors being more akin to Xanthites, though my knowledge of them is as old as 3rd Ed TT. Ah, they are now Excommunicate… http://wh40k.lexican...rs#.UWdqHqJJNWJ so maybe an Oblationist would consider them as foul (if not worse) as Xanthites? 40K philosphy is not my gig, so I can't confidently say.
Something I thought of, purely from a role-playing perspective: what do you intend to do when PCs reach 100 Corruption? I know this means they have "moved beyond the scope of Black Crusade", but If they are (truly) dedicated and loyal servants of the Emperor they would rebel against apotheosis. Of course that would be the irony, now wouldn't it? All this pure-intentioned work done in the Emperor's name, but the Ruinous Powers claim you as the reward, MWUHAHAHA!
About Corruption: many of the examples for awarding it are from the perspective of "bad guys", like it being handed out for "sowing discord among the followers of the Emperor" and other such. You may want to give this section (pg 288) a look as you may need to redefine the acts that merit Corruption awards. And, if (as you say) PCs will struggle to remain Unaligned, without some adjustments the PCs may find themselves "earning" (possibly) a fair bit less Corruption. I imagine a PC who, initially, kills his foes with a sense of duty, the result being little (likely zero) Corruption, but as the months and killing wears on the PC comes to get a "sick" sense of satisfaction from his blood-soaked blade skirling across flesh and bone. Does the chime of blade on bone make the PC grin with perverted pleasure (attracting the attention of Slaanesh), or does the PC measure his success by the depth of the bloody puddle collecting at his feet (attracting the attention of Khorne), and so on…
These are things that you (as GM) could secretly keep a record of (a confidential tally of unconscious dedications to the Ruinous Powers) that you later use when awarding Gifts of the Gods and other such.
It could just be that the very act of entering the Vortex changes all perspective, and Corruption comes as naturally to "Acolytes" as it does to CSMs and Heretic Disciples.
A small point, but one worth mentioning: you might consider Legion Weapon Training and Astartes Weapon Training to be one and the same.
Like Ancient Warrior, Child of the Warp might be an issue (validating) at CharGen.
Without reading each Skill and Talent individually, I think that's about it for initial stumbling blocks. Considering that Talents are tiered, with some requiring prerequisites, and their lesser to greater XP cost being determined by Alignment I don't think there are too many other issues with regards to Talents. However, "struggling to stay Unaligned" means it will be harder to get these Tier 2 and Tier 3 Talents. You may have to consider XP awards on a PC-to-PC (individual) basis; some Players will give in slowly (if at all) to one Power or another, while others might see aligning themselves with a Power relatively quickly as a means of better meeting the letter and the intention of their stated Mission within the Vortex. Handing XP out in a "generic" fashion (X amount per session) may lead to PCs quickly aligning themselves, while handing out XP based on RP would allow Players to "pace" their PCs' plunge into hell. However you work this out, I'd suggest sitting down with your Players to discuss this aspect (XP award) of character advancement before the games begin. Or, you could impose an XP minimum (say 3500-4000 XP, about 10-12 sessions @ 400 XP per) that PCs must reach before "allowing" themselves to become Aligned? Perhaps introducing an XP penalty (100-150 per session) for becoming Aligned too early?* Or, you could have this system in place, but keep it secret from the Players; one PC notices another's sudden and rapid advancement in Characteristics, the acquisition of Skills/Talents, and wonders why; does he remain true to the Mission, or does it become a free-for-all as he/she seeks to become Aligned, a sign of personal glorification, vanity, and a clear indication of self over the big picture?
*This could backfire, and you could end up with PCs of wildly varrying XP totals, meaning a possible strain in inter-warband competency, and difficulties (as the GM) equalizing encounters (social and combat-related).