Another question would be the origin: DE or MX ? If MX, since which year?
Often we change the origin to the new country when there is a local restyling done, but that VW kept an overall look quite similar until the end.
So for this one I would use only DE as origin.

The jury is still out on whether these should be listed as 2004 though

You mean changing the few 2003 Última Edición to 2004? Not many indeed, for the four of them I'd do that manually anyway
https://www.imcdb.org/search.php?resultsStyle=asList&sortBy=0&yearFrom=2003&yearTo=- &makeMatch=2&make=vw&modelMatch=0&model=%C3%9Altima+Edici%C3%B3n&modelInclExtra=- on&mk=&origin=&madein=&madefor=&role=

See https://www.imcdb.org/vehicle_257971-Volkswagen-Sed%C3%A1n-Typ-1-2003.html

They are not too many, should a mass update be done? (after your trip, of course)

2001 Toyota Altezza Gita [XE10W]

Delete Made For J From Japanese market
https://www.imcdb.org/search.php?resultsStyle=asList&sortBy=0&make=Toyota&model=- Altezza+Gita

Don't Delete Made For J in USA
https://www.imcdb.org/vehicle_1186970-Toyota-Altezza-Gita-XE10W-2001.html

Another USA origin:

https://www.imcdb.org/search.php?resultsStyle=asList&sortBy=0&make=Infiniti&model=- QX60
https://www.imcdb.org/vehicle_1782426-Infiniti-JX35-L50-2013.html
https://www.imcdb.org/vehicle_1835973-Infiniti-JX35-L50-2013.html
https://www.imcdb.org/vehicle_1807485-Infiniti-JX35.html

Updated

The model origin of second gen. Honda/ Acura NSX is USA, Japan only developed engine and transmission

Development of the engine, hybrid system and transmission would be done at Honda's Automobile R&D Center facility in Tochigi, Japan, while development of the rest of the vehicle was concentrated at the Honda R&D Americas development center in Ohio, United States.

https://www.imcdb.org/search.php?resultsStyle=asList&sortBy=0&make=Acura&model=N- C1
https://www.imcdb.org/search.php?resultsStyle=asList&sortBy=0&make=Honda&model=N- C1
https://www.imcdb.org/vehicle_893014-Acura-NSX-Concept-2012.html
https://www.imcdb.org/vehicle_525885-Acura-NSX-Roadster-Concept-2012.html

All Mercedes-Benz Metris are assembled in the USA according to Wikipedia:

https://www.imcdb.org/vehicles.php?resultsStyle=asImages&yearFrom=&yearTo=&makeMatch=- 2&make=&modelMatch=1&model=Metris&modelInclModel=on&modelInclChassis=on&mk=&origin=- &madein=&madefor=&role=

To me generic codes are better than too-specific ones, as I already said for other vehicles.
same for Mercedes, people will search for W121 if they want that model, and then may miss all these specific ones. If one wants just a body style, there is a filter for that. And I'm not sure that having a way to filter on engine type is useful.
A solution would be two codes : a "generation" code for the generic code and then use the chassis field for the specific ones. But I don't know if it is good to add even more info or if it makes more difficult to maintain.