psykers in w40k are very tricky to play. The rules are brutal and lethal, about as dangerous for the caster as for his opponents. What you do as a psyker is open a conduit to the warp in order to use your powers. The warp is inhabited by shitloads of very strong and very nasty demons, looking for a way into the prime material. Only those that are strong enough are trained and conditioned to use psychic powers, and that training and conditioning leaves them damaged in body and mind. They are universally feared and reviled throughout the imperium.
Don't say I didn't warn you . But you're more than wellcome to play one . Do you have access to the books? If not, I'll type a long post tomorrow and we'll get cracking at char creation.
If he manifested during combat he'd get a bullet in his skull from his squadmates or from the comissar . If he was really lucky they'd beat him up and hold him in a cell under heavy guard untill he could be collected by the black ships and sent to Terra. After that he'd be assigned a task. That could be with an assassin as backup (and safety net to but a bullet in his head if he s up) .
I take it you're primarily interested in playing a telekinetic?
Nah, just go for the option I posted. I don't really care about such silly things as stats unless you go ludicrously high or low
So we have shayuri as bodyguard/assassin and jkason as a psyker.
jkason : you need to pick an origin world. I'd type a huge post but it's better if you just read that part in the PDF. Don't worry too much about optimising your character, just go for what makes you feel 'waaw this is cool'