Both good points. I would assume you're going to have to firestop every penetration between tenants.Are there firewalls you are penetrating?
I think running across the roof would be less manhours than going through all these businesses in the ceiling.
Have you actually looked in the ceiling? Is it a straight shot through the ceiling or is there duct work and "stuff" in the way?
I wouldn't bid this without a thorough look over the ceilings no matter how much of a hurry they are in, you could take it in the shorts