Also worth bearing in mind that a chain is only as strong as it’s weakest link-
The ‘4 custom cars in a nice building’ also suggests there’s going to be an up/over door or roller shutter access for the cars- I’m in the UK also, so it’d be pointless suggesting locks and fittings that won’t be available your side of the pond, but he’ll have to consider all doors and access equally to make it effective.
It’s horses for courses as the saying goes- different types of lock suit different types of doors and applications. A large sheet steel up/over door or a roller shutter need totally different thinking to the hinged wooden entrance/exit door.
Also, it’s worth checking the entrance/final exit is a good solid timbered door, preferably hardwood, as it’d be pointless going to those great lengths to fit additional locks if it’s a hollow door you could stick your boot through with a single kick! The thickness of the door, the width of the style etc are all things to consider when choosing a lock. Also it’s essential to fit hinge bolts on the rear side of the door if it’s outward opening with exposed hinges- side garage doors often are outward opening here in the UK.
I’ve seen Bramah MD27’s shoehorned into hollow internal doors where there’s only a couple of millimetres of veneer either side of the lock- a tribute to the carpentry of the person who fitted it but that’s about it! a classic example of getting it wrong and leaving someone thinking they had the best but actually had nothing. I’m sure all the guys your side of the pond can make some good recommendations 🙁happy):
