sfx2000
Part of the Furniture
I haven't considered pfSense as an AP os. I just looked it up and it seems it would be quite risky, pfSense's own docs say that don't recommend using it as an AP OS. I think it has a high risk of being buggy.
Just to recap...
Break things out and keep it simple - simple is better in the long run...
Router to the outside world - pfSense is a great choice, Microtik and Ubiquit have some interesting options if one doesn't want to roll their own with pfSense, but pfSense is a very powerful and stable platform.
Layer3 Managed Switch to build out the VLAN's for each client
AP's (just as AP, not router/switch/etc) for each office/floor/org