Good info sir! Yea I'm sure all the have to do is use tesselate their current standard car models to the same quality as the premiums and just create the interior views, update the headlights, back lights and so on. I don't think it would take as long to create a premium from scratch like you said the base models is what takes probably the longest.
And the car's physics engine has to be updated to the current.
Not quite - PS2 models, really no matter the game, have had to be optimized for in-game use, and tessellating, or any form of smoothing really, requires good edge flow. I could blow 70 pages of forum space on the topic (but I won't, google 'good 3d topology' if you're interested), but the point is there'd need to be some cleanup before they could be smoothed and cut into panels. Headlights can be a pain or they can be easy, depending on how the shapes interact. Several concentric circles (think old Audi TT or Veyron) in a smooth shape are easy mode, they work nicely and easily, but lights such as the Zagato Kanto are a very difficult to work with because they're not as simple, and any errors in modeling will cause lighting/shading errors in game.
Also, the physics won't need to be changed much, if at all. It's all values for each car (spring rate, spring length, etc etc etc), just run those through calibration and testing (what they would have already done with Standards) and make sure they're good, and bam, done.