I think it would be nice if there was some drop down list or similar with pre defined options when adding/renaming cars plus the options to type in a new make to the site, sometimes there is spelling errors (like Massey Ferguson / Massey-Ferguson) that could be skipped with such feature.
Maybe a similar system like that google have if you know what I mean?

Also when having predefined makes and models, we could maybe have a small Wikipedia-like info page about that model with info more interesting to us (than the actual Wikipedia page) like MY changes, color codes etc.

With such info page it would also be possible to see all rebadged vehicles under one page that can't be found in the present system (like Talbot/Simca/Chrysler).