As for re-creating liveries, as opposed to originally making one? Here were my ideas:
-German cars: FEISAR
-Japanese cars: AG-Systems
-American cars: Auricom
-British cars: Icaras
I'd love to make a Triakis livery for any Australian cars that get in, too. But in the meantime, here was another idea:
-BMW M4 Gr.4: "Need for Speed: Most Wanted (2005)" livery, albeit potentially with added sponsors that use the modern "Need for Speed" logo/font, the modern EA Games logo, and logos for Criterion Games, EA Black Box, and Ghost Games.