I'm not really sure about this one. On one hand, i remember games (like the first Rollcage and Wipe'Out" games, and others too) where you had one specific pilot for each vehicle, and i was never a big fan of this. I even ended never using some of the vehicles because of the pilot!
On the other hand there are games where it always felt right. The best example i can come with is -watch out, oldie incoming- Jet Rider (i guess it was called Jet Moto in English), with 20 pilots on each race, divided on four teams, some being good almost everytime, some being really crappy -yet capable of amazing results once in a while- and others making average results most of the time. Each championship on this game felt different from the others, sometimes you could win the whole championship without winning every race, and sometimes a single accident could ruin the whole season. I know it had a lot of bugs and didn't age too well (it's one of the first PlayStation games after all), but man, i still love playing this game even now!
Anyway i think Grip should definitely have racing teams based on different car manufacturers, but i'm really not sure about the pilots thing, though i must admit that if it's done well, it can really be great. And with many pilots it's getting interesting to know who's who.
I guess we just need to have faith in the Dev team, so far you've done a really good job!