Open services (banking/sensenet/genetek) in Red Zone (albeit at a higher price). Disallow travel by mag-lev unless the character has clearance. If a character without clearance travels by taxi and gets scanned by "the authorities" or a security checkpoint then they are fined and deported back to the nearest zone that they have clearance for.
It would work in a top-down manner, with clearance levels granting access to the zones below them.
Immigrants/bums/gangers - Red Clearance
Wageslaves/Low-level corpo rats - Gold Clearance
Mid-level security/corpo/celebrities - Green Clearance
High-tier security/corpo/celebrities - Blue Clearance
This would open up opportunities to use stealth to bypass it (excepting checkpoints) or for technicians to provide forged passes. I imagine the forged pass would be a skillsoft that you can slot. It would also allow the players who want to be grimy gangers and never interact with higher society to do so.
Might need to move Withmore Wholesalers to Green Zone, so it doesn't cause problems with couriers with Gold Access getting into Green.
FIXED FIXXERS
Let the prices in Gold Zone be the baseline and raise the prices of those items by 20% in Red Zone (or whatever math works) and lower the prices of those items by 20% in Green Zone. So a character (fixer) with connections to access zones above Red Zone can procure these items and then sell them at a marked-up price, profiting, but still providing them at a lower cost than prices in-zone. Put neXus in Gold Zone to account for the loss of access to armor, with Protek staying in Green Zone to be the premium gear.
It would be a lot of relocation of items, mostly, and some new rooms (Red has empty lots), but it doesn't need to be fancy for the mix. The structure would give fixers a way to work the system (without waiting to resell hand-me-downs) and create a new money outlet for programmers/technicians.