Personally, I would only carry a firearm on my person, not in a bag. You won't hurt the gun or holster if you roll onto it, although it may be uncomfortable.
People who spend alot of time in a vehicle sometimes mount a holster in the vehicle or place the gun/holster in a secure place in the vehicle when they first enter it. Since the gun is then not on my person, I don't like this idea.
You could carry a 2nd, smaller handgun in an ankle holster (to provide better access when sitting in the van), but I don't like ankle carry for my primary gun. An ankle holster is also more likely to be revealed when crawling on the floor than an IWB or OWB carry.
I generally don't spend much time in a vehicle, but when I do, I have easy access to an edged weapon. I have an ESSE 3 fixed 3 inch blade which attaches to the seat belt. A car-jacking is likely to come through the driver side window, and an edged weapon works well with a close-contact attack.