Some 1997 Formula One cars - I tried to make the sponsors fit:
What if BAR entered in 1997, with Suzuki engines?
Lola-Chevrolet - After the collapse of Mastercard Lola, Chevrolet joined using a more refined version of the 1997 car, with new Chevrolet engines. It was a lower midfielder.
What if Honda joined, not as part of BAR, but as it's own constructor? Based on the Castrol NSX
Lamborghini Valvoline Racing
What if BMW instead joined as a constructor of it's own?
What if Toyota joined in 1997 with a Fujifilm sponsored car?
What if Dodge joined as a response to Ford and Chevrolet joining?
What if Mazda joined, with a rotary engine?
On a side note, if anyone's looking for ideas for fantasy skins for AC, these might be up your street. I'm quite bad at skin creation.