Then maybe the good solution would be to have two codes, one named "Generation" (where we can put the generic one) and the other being the current "chassis" code, more technical/specific.

Agree on the third option, list both codes, but maybe the specific codes can have links too?
Or put the option to Advanced search for a vehicle section to make a page looks like this
https://www.imcdb.org/search.php?resultsStyle=asList&sortBy=0&make=Honda&model=E- J6&page=1
https://www.imcdb.org/search.php?resultsStyle=asList&sortBy=0&make=Toyota&model=- SXV20

I believe the codes have some values on site, especially for those like me who will take a look at these specific codes and try to study them.
For me, the codes not only represent the uniqueness of each model in their market but also take me by surprise sometimes when I try to dig the codes for some models in our market.

For example, Honda’s EJ* can be referred to as sedan, hatchback and coupe, and we received EJ6 in this case instead of simply EK. If not for IMCDB listed these codes, I wouldn’t even know that much.

I think I already posted this somewhere, but I'm not sure where, and this issue should be solved
Lately there were some highly specific chassis codes entered (or just suggested) for some Toyota models
e.g.
https://www.imcdb.org/vehicle_1944715-Toyota-RAV4-XA30-2011.html ASA38 vs XA30 - the second one is used on Wikipedia for example: https://en.wikipedia.org/wiki/Toyota_RAV4
https://www.imcdb.org/vehicle_1470153-Toyota-4Runner-N280-2017.html GRN285 vs N280 - here also used on Wikipedia: https://en.wikipedia.org/wiki/Toyota_4Runner

Previously we already had these issues with the Land Cruiser, that we listed with the generic codes Jx0 where x was a different number for each generation: https://en.wikipedia.org/wiki/Toyota_Land_Cruiser
To me, these specific codes do not have much interest in search & lists, since only a few cars have them.
The generation codes is more useful to be able to group/search vehicles by generation easily without having to rely on years (since sometimes these even overlap).
What do others think?
- use only the generic generation codes? (keeping the specific ones in the comments, with VIN info)
- use more specific codes? (losing the easy-search)
- use both, but then we would need an additional field for the specific code, without link, like the extra info compared to the model name.