Well, it's an ambitious undertaking. However, it sounds like a very neat idea.
A potential problem is the hacking rules are designed to be fairly abstracted because usually that's a sideshow, rather than the focus of gameplay. But it's better to start small and work up, so I wouldn't suggest any custom rules to make things more complex for the sake of engagement's sake. Not out of the gate, at any rate.
Some key things:
Certain hosts happily issue marks to anyone who wants to enter. The kinds of places that conduct e-commerce, for example, WANT public traffic traipsing around in their hosts. (See the example of the Seattle Public Library on pg 220, SR5).
Of course, marks only flow upstream, not downstream. So once your runners have a mark on the host (either because it's welcoming them inside, or because they illegally hacked entrance) that does not mean they also have a mark on everything IN the host (this is a major difference from 6we, btw). Every icon, be it a camera, maglock, or datafile, has to be individually marked (by EACH runner who intends to mess with it!) Also note that any important/restricted/classified files should be protected by encryption (see Crack File, SR5 pg. 238) and possibly even Data Bombs. Even the Seattle Public Library is going to protect files that the mouth-breathing public isn't welcome to just download willy-nilly.
Again, the hacking rules are written in such a way that a solo hacker can reasonably get the job done. If the whole team is going to be hacking, you might want to engineer some challenges that require teamwork. Such as, require various hackers to each penetrate separate (but related) hosts to satisfy what are in effect
two-person integrity safeguards. For example: a system might be set up so that only "authorized" users, one each in hosts A and B, authenticate a command simultaneously in order for a data vault in Host C to grant access to a third user.
