Hmm, I should perhaps try to arrange from them to have an NPC or two on board with them. They could find their old Sergeant or even 2Lt. who was captured after the ork landing, and then left behind when the PCs and company escaped from a Dominate base (yes they were tricked by the false Inquisitor and captured).
After playing with them tonight though I realise they can pull off some amazing combats sometimes. We played the Killswitch scenario where the squad is sent to recover Ordinatus intel and take out an enemy tech priest. They managed to sneak up to the place, pick the lock on the bunker, take out the first Servitor, then took out 10 servitors at once before they even had a chance to act except for the last one, whom they managed to dodge the self-destruct blast.
When they opened the door to the library Mech-Deakon Klax let lose an overwatch with bolt pistol and a shot from the plasma mechandrite, wounding the Heavy and suppressing him and the Operator. However, the Weapon Specialist charged the Klax with a Hunting Lance (yes the explosive one that Roughriders use), knocking him down and stunning him for several rounds due to the Concussive effect. Then the Weapon Operator used his Plasma Gun on maximal and completely annhiliated the "renegade" tech priest. To cut the combat short I assumed that the default setting for his servitors was to self-destruct if he died, so they did (while in melee with said Weapon Specialist, but he managed to dodge away instead of dying.
The combat against the Stormtroopers started with a dialogue, but when the players refused to let them into the bunker to check up on the Mech-Deakon, they decided to try to take the bunker by force. Bad move. The Stormtroopers had no chance and got gunned down by the Heavy and his Heavy Stubber, or taken out in melee by the Weapon specialist and his twin chainswords. The Operator stayed in the bunker below and checked up on comms etc and was not even needed.
So the PCs had the great defensive advantage of the bunker, but they were still able to take down 5 Stormtroopers at an alarming speed, taking no damage.
So yeah... maybe they will pull it off without too much trouble, but I assume they will do some collateral damage to the control panels inside the Ordinatus first.
I am also very exited about the Commisar Salieri meeting (I'm still gonna pull off the Samuel L. Jackson routine), but I assume the group will claim that they were working for the Inquisition and show off the three cases they got (from random rolls on random gear table) and the Assassin gear they got. Saleri might even believe them if they roll well enough, I think the Inquisition stuff should give a +20 bonus at least in their argument that they were driven by the will of the Emperor. Although they probably suspect something is fishy, and have noticed Fordham's weird behavior and the fact that they were shooting at Imperal units.
well don't forget the commissar's pet pysker and her mind scan power, she can tell they weren't working for the inquisition so that argument can be shot down in flames (and get a comrade or two executed for lying to him)