Ok so, I'm just trying to get a general idea on if this is possible and how it'd be worked into BC. One of the players in the group I'm apart of is a Tzeentch worshiping Psyker, and atm he is wondering if he can take the Sorcerer and Master Sorcerer talents from the RT or DH games as well as the various spells and such therein. I'm not the GM, but I'm trying to get a general view on this and how it would be made to work. I've thrown around some ideas though, but want to hear what you all have to say on this..

personally I wouldnt mix and match stuff like that. It gets messy.

I have a player that currently is trying to sweet talk me into letting him play a Honsou type iron warrior.. but he "needs" the mechanicus implants to take his servo arm. this is with him building his Iron Warrior as a Champion and fleshing him out to be the warband leader. I dont really like this idea being in a game Im running because it lends itself to openly for him to later on whine or whatever with " well its only one other mechandrite"....or trade:armorer, things that will start stepping on my hereteks toes and stealing the limelight hes good at.

this is the second time hes approached me with this. the first time was he wanted to incorperate things from the techmarine from DW with the champion in BC.......like I said this can complicate stuff very messy very quickly..if you have a concern about this then let the GM know your thoughts, but its gonna be his call in the end.

This particular instance of mixing probably shouldn't be done. Sorcery is already implemented in Black Crusade - you simply use Blasphemous Incantation when manifesting a power.

Other than that, I rather disagree with Adept Orcadius. If a player is prepared to pay an appropriate price for something, I'd generally not restrict them. For example, I'd be absolutely fine with allowing the Iron Warrior to trade his archetype ability for a servo arm and the later mutations for a single 'dendrite each. This way, the player gets to fulfill his concept while game balance is preserved and the heretek doesn't need to feel overshadowed.
After all, the game is about having fun, not keeping your players on the straight and narrow line of Proper Gaming .

The BC Psyker starts off with a Psy rating of 3 which is the same as a starting Psyker + Sorcery talent from Dark Heresy, IIRC.

I agree with the mixing of Dark Heresy Sorcery with the psyker rules in Black Crusade. That type of sorcery is covered from the aspect of a inquisitor acolyte or radical inquisitor, not from a chaos worshipper. Besides the powers in BC are more tailored to open worshippers of chaos.

So far as the chaos techmarine goes I'd work on a variant archetype of a chaos techmarine. Definitely don't let him use the champion archetype.