I know very little about modding, and was wondering how easy (or otherwise) is it to export Automation models to GTA V?
Very very difficult. To the point of might as well model the whole car from scratch instead, would be easier. Safe assumption to make in all these “could it be imported to game x” questions is that it would’ve been done already if it was doable, because everyone wants to get new cars for their favorite game.
They don’t even have interiors to begin with, but ignoring that, they’d still have no LODs, opening doors/hood/trunk, etc. Really not worth the effort in my honest opinion.
You’d have to think of stuff like, how does the game handle the rigging of suspension, can the existing suspension stuff in an Automation car be used in any way or does it have to be completely redone, how would you model an interior that fits the body and chassis while also fitting the game’s player characters, how much of the engine model you leave in (lots of polygons there that you’d never see in GTA), replacing the wheels with the wheels from GTA (because I guarantee you Automation wheels won’t work), making holes in the body for the fixtures (because Automation has its own special way of doing them that won’t work in GTA).
The list would go on but you get the picture. Same sort of stuff for any other game and different games do things differently so they come with their own set of problems.