For Achak's observation, I think they're pulling an Ollie North, and that the briefcase contains the backup. It's big for data files, and paper files are a rarity these days, but that's what the dialog seems to indicate.
Mercer is basically turning off his SIN transmission, and switching all of his gear to wireless on, running silent (even the stuff that was previously not running silently, per the house rules on insta-locating non-hidden devices). This excludes the drone outside the window - a sudden influx of new hidden devices might alert them to impending action, and the van being outside 100m as it is all that gear going hidden should go unnoticed. He's also getting his ballistic mask ready to put on. He'll probably open with Vera on the remaining guard in the parking lot and the mask might give too much warning, so he'll take his shot, then put it on. All of the other guns besides Vera are staying wireless off for now. The Roadmaster is staying Wireless on, non-hidden as well as it couldn't hide if it wanted to. He'll also grab another Thermal Smoke grenade if he has time, but he's doing an awful lot, so he might ask Nori to grab it for him from the smuggling compartment. Or you can just say the action happens too fast and he doesn't have time to grab it - I'm fine either way, it's a nice to have but not critical.
Just in case his dialog is unclear, he is suggesting Nori use the Target Device action (Rigger 5.0 pg. 30), or if her EW is suck, then just put AROs for devices she spots and identifies in the matrix so that the aforementioned shooting through walls can be done. He's also suggesting that he'd like to take the enemy decker out of action ASAP, so his location would be a priority. Inside, they might want to deal with the magical types first, but I'll leave target prioritization to them.
Also, he is thinking that the best opening move for the indoor team might be a grenade through the open office door, assuming they are still open, otherwise you might need to open them yourself.
Mercer's other thought would be to herd them into the hallway (shooting through the windows with Vera should get them moving in that direction, especially if they don't suspect there are people inside the building). Would Mercer see this as a potentially more viable strategy than announcing the existence of the breaching team as an opening maneuver. This might qualify as a Crossfire situation (herding them into a kill-zone). If they open with the grenade, then we could still use it as a "Chuck and Charge". Mercer could coordinate using the Fly-spy as eyes and ears. I'll roll Perception for his general looksie for potential problems outside, and SUT to see which he thinks might be a better tactic, and we can roll for whichever one we decide on. Mercer has a good leadership skill, so he can cover for one person that has the lowest SUT dicepool (Int based).
Perception [INT 5 + Perception 6 + Visual Enhancement 3 + Spec 2]:
16d6t5 4 Abysmal as far as dice pool to success ratio, but 4 hits sees quite a bit, so I'll take it.
Small Unit Tactics [INT 5 + SUT 5]:
10d6t5 4 That's better. He should have a pretty good idea on what tactic would provide the best odds of success.
If we decide on running away, I just want to remind folks that we have two vehicles, so the Roadmaster can distract and cover while Nori's ride picks up Achak and Becca. But it looks like we ain't planning on running just yet.