I'm thinking that I might add vehicles as a form of creature. That way they can be targeted in VATS and be interacted with by other NPC's, like horses.
Hell, why not add horses too? I mean it wouldn't be much of a western without em.
I was reading about the two mods here:
http://www.fallout3nexus.com/downloads/file.php?id=3330
http://geck.gamesas.com/index.php/GetSitting <- Can anyone help me confirm whether this script works or not for mounting creatures in fallout? (I just checked it: it should work... I think.)
Plus, there are several articles about creature mounts at the TESIV Construction Set Wiki.
http://cs.elderscrolls.com/constwiki/index.php/GetSitting
http://cs.elderscrolls.com/constwiki/index.php/Making_Ridable_Creatures