Without giving the store away, almost all VIP, VVIP and support staff flights will have already been precleared. Flights are scheduled a "Slot" time to arrive, offload and then the move the aircraft using a "follow me" vehicle to an assign parking spot.
If you take a look at a runway map of ORD, 32R/14L, 27R and mega hold pad (AF1 will park there) up north are the designated parking areas.
Yes, the FBO area will be used as it gives the easiest access to 190 and the Kennedy.
Normally when AF1 arrives, arrivals and departures stop for a short amount of time. This will happen for him, but it sounds like when any other HoS arrives, it will be business as usual for flight ops.
I understand there are security issues about many of the details.
But, I've seen VIP aircraft parked in that area before. And there are decent places for spotting. picture taking, etc nearby.