I'd recommend something like this for simplified hacking:
a) the hacker needs a roll (or maybe an extended test) to get into the computer that controls the doors (cameras, etc). He needs another roll for every action he performs (open door, redirect camera, access data, etc). He does not need another roll if he uses the same device a second (or more) times. All of these rolls are independent of where the hacker is physically located.
b) every time the hacker makes a roll, the hacked system makes a detection check (against whatever hacker skill or attribute; maybe the rating of his stealth program). What happens if the system succeeds is largely up to the GM, or can be predetermined (this is what the SR3 security sheafs basically where:
- the hacker's DCs to do anything go up by one. This is the simplest outcome.
- the system detection roll improves by some number
- the system launches some form of attack, eg:
- crash one of the hacker's programs (preferably the one he was using to perform his action): roll system's skill vs hacker skill (add programs to either check as you like); if the computer wins, the program crashes and either cannot be used in this run anymore or has to be reloaded or something.
- the system tries to trace the hacker: again, a single contested roll. If the system wins, it knows where the hacker is and can either upload malicious software to his deck or try to fry it (and the hacker)
- the system (or an alerted security hacker) attacks the hacker: this should be run like a combat, and should be timed to coincide with a combat the rest of the group is running into (eg: the alarm goes off, and the runners are attacked by guards/drones, while the decker suddenly encounters black ice!). This way, you can run it all as one single combat (with a single initiative count), and no one will have to wait too long to have an action. Better yet, the hacker may be forced to split his attention between the ice and other tasks the rest of the group needs him to do. Fighting rolls may or may not trigger further detection rolls. Depending on the ice, the attacks may damage the persona (or avatar), they can damage the deck, or they can damage the hacker straight. Black ice might damage both persona and hacker. Psychotropic ice might just do stress damage, and if the hacker passes out, his mind gets reprogrammed...
- the system shuts down. Security is compromised enough as that the system sees a shutdown as only way out.
This example system lets you ratchet up the attention level as needed. The hacker requires comparatively little overhead to get started, and he doesn't have to sit around and be bored while the rest of the group fights.