@Avanhelsing Patch just offered a plan you could run with, or climb up the side of the building while he and Owl distract the guards with at least. Archangel has identified a window access up there which could be used to gain entry to the building, then it's just a matter of stealing as much high-grade weaponry as you can carry and planting explosives anywhere marked 'Flammable: Do Not Plant Explosives Here' before sneaking out again.
This should run as a high stealth mission, with lots of dodging guards and watching out for cameras, but feel free to make as much noise as you'd like so the other two can storm in and save your ass from toasting.
This should run as a high stealth mission, with lots of dodging guards and watching out for cameras, but feel free to make as much noise as you'd like so the other two can storm in and save your ass from toasting.