And things get double- and quadruple-checked at every stage of the game. "Is this the thing we want? Is this the address we want? is this the client we want?" While I absolutely do not prevent such a heist from taking place, it is absolutely a full-bore shadowrun with multiple, even dozens, of hackers involved, because of many things that need to be set up and maintained. Add in that even just setting up the false corporation doing the purchasing is going to require multiple 'runs, because that's getting not just triple-checked, but physically checked.
I can think of several ways to do this sort of thing, but even the 'easiest' one is going to involve hacking the Host of the closest military site with the gear you want, to plant ID information in that limited site to assist the intrusion of the entire team. Then it's a variety of cons and hacks -- planting authorization to check out the piece of gear, planting a reason for it to be checked out, the face checking it out, the mage modifying the memory of the quartermaster to make him not remember that he checked the thing out, hacking the quartermaster system to erase that part of the log, hacking time in a shop to disassemble the thing, the gunbunnies and/or rigger taking the thing apart, hacking the shipping to send 'parts' out to places -- and then redirecting those shipments several times to 'lose the tracking'.
And that'd be just for something limited in size, like a single Thunderstruck gauss rifle or one suit of milspec armor.
Getting multiples would start out by putting together a company that'd be authorized to buy the things, going through the verification from the manufacturer (including a physical visit from an inspection team), all that. Essentially, you'd need an organization to pull it off ... sounds like organized crime, doesn't it? If/when you get a hold of milspec gear, there's a good chance that that's where it came from. Another potential source would be a recently (and possibly violently) defunct military organization, such as a merc group.
But yes, you can do a lot (including, possibly, generating a Thor shot) through the Matrix. It's my belief that the decker is the most dangerous person in the group, and always have been. But like with all the other options, you can't get everything you want just by manipulating the Matrix.
Sorry.