Putting too much info is not always a good thing.
There are comments for thing like range year. I am not sure that it would be useful to have also an end date. I could add it, that's not a big problem. I already did it for movies entries, since series need an end date in addition of a start date.
Model type or series number can be put in what is currently called "Chassis code". For Cadillacs we were not using it, but we could do that.
Model/series name goes to model name field.
Then we miss the sub-make and sub-model as you described it. I could add such fields, but would they really add something compared to the current solution, where these two info are put as "extra info"?
For the body style, it is currently selected from a list. If it was as a free text, it would have two problems:
- translation in French (and in German if people use it), or in English in the case of French cars. What about the name of cars in other languages then, if we take the body type given from the maker and not a standard type from a list?
Additional comments can be put in "extra info" field, but also in the... comments. At first these were added for that, for allowing people to give some info about the cars, not only for discussions