I was thinking, Before we were talking about how Marines are often 'called in' to assit inquisitors in special situations. Marines are super human and the pride of the imperium and I can see all sorts of reactions from taking orders (resentment, anger, apathy, whatever) So to represent the Marines 'individualness' here is a reaction chart. (it would make the Marine act in a special way the whole game opposed ot complete control by the player)

Roll 2D6 (notice, the ends of the spectrum which are rare are more extreme where the center is less extreme)

2-3: 'You killed Brother Kenneth...!' The Space marine recognises the Inquisitor he was sent to work with and knows he was the cause of one of his battle brothers death. The Marine is put under the control of the GM and must make every attempt to incapacitate the Inquisitor character to take him to back to base to answer for his crime.

4: 'Why was I called out for this???' The Marine feels his time is being wasted and he has no reason to be in the area. He is totally not into the situation and just wants to finish up and go back to base. The marine halves his speed and actions at all times unless defending himself in combat.

5: 'I am on my way' The marine was on another mission and will arrive as soon as possible. The Marine shows up D3 turns after the game has started. When he enters, he comes in on any board edge.

6: 'Eeeehhhhhhh, if you say so....' The Marine questions the Inquisitor's ability to lead sometimes.Every turn, have the Inquisitor make a leadership test. if you pass, the marine will follow orders. If you fail, the Marine will retreat to a secure location until acceptable orders are given (next turn the Inquisitor passes a test)

7: 'YES SIR!' The marine has no issues and follows orders with no problem.

8: 'Bah, I have fought hundreds of these guys, let me do it.' Every turn, the Marine takes a leadership test on his leadership. If he passes, the Marine will do little but follow the Inquisitor and defend himself. If he fails his leadership, he looks to the Inquisitor for guidance and follows orders.

9: 'It isn't safe for you' The Space Marine feels that the area isn't safe. the Player nominates a model and the Marine GUARDS him. The marine must stay within 2 inches of that model at all times and may only support or protect that model.

10: 'You blasphemous scum!' The Marine feels like the enemy needs to be cleansed from existance. The Marine must use all actions to attempt to incapacitate the enemies without killing them. (of course they should be brought in for proper executions) They have to always make full movement torwards the enemy and must be attempting to attack or subdue the enemy.