There are many things to be done, some of which you havent mentioned like maintaining proper naming of cars - for example, when a Honda NSX Mk II came out, all previous NSXes had to be given the "Mk I" hint to make it easier to differentiate them. Same goes for model lines where internal chassis designation is used - for example, all audi A6es have to be given the "C5, C6, C7 etc" AND the "facelift" designation in addition to that, where there are mid-generational refreshes.
For some cars I can't even figure out how many mid-generation refreshes are there and which ones are refreshes and which ones are proper new generations. Maintaining this all is hard.
But the upside is that FastestLaps is designed to NOT have too many car pages, because each page represents a model range with multiple transmissions and "sub-trims".
Also, big positive in past two years (since the new data system) is that (almost) everything that is added is actually correct - there are virtually no fake or incorrect or reference-less data added in past two years. There used to be a lot of garbadge performance data and much of it, like Inline pointed out, is still not removed. But at least new garbadge data is coming in at a much slower rate then in past :D