Seems like the sense-able thing to do. It's not going to hurt the cars or truck to be parked in the driveway and I'm sure not going to pay to store my equipment if I have a garage.
Except UV will deteriorate the paint, rubber & interior.
If left in the same place day in day out UV will also cause a hard patch on the side walls of the tyres which is why they make wheel covers for caravans.
The trailer & gear would go out to work every day ( one would hope ) but at least one car will not as your bum will be in the truck.
The gear on the truck are depreciation . Tax write off items, chances are the cars are not and the work gear most likely gets turned over a bit faster than the cars and is a lot cheaper to replace.
Pallet racking can be installed in the garage so that the nose of the cars is under the lowest shelf and you can fit a lot of gear on pallet width shelves thus you are getting double use of the floor area.
Old pallet racking is very cheap and is self supporting so if you have a work bench at one end it can be installed a foot or so back from the bench you just have to be able to get in & out of the cars without banging your head.
I have done a lot of similar "bridge" style installations in restaurants store rooms & work rooms and in one case we moved the wine storage from the wall to overhead, stored all of the dry good over the top of the managers desk and basically turned a disaster of a storeage space into a working space & I get free lunches whenever I go there they are so happy with the results and it cost peanuts when comparred to expensive wall shelving.