Instead of more cards , have you thought abour giving the cars themselves some special abilities? Such as allowing one of the cards to play 2 mg's each turn but no other weapons or allowing 1 to have some sort of componet armor that could protect its tires or driver instead of just useing the armour for the spacific sides that is stated on the armor card. maybe allow the flame car the ability to take a discarded flamethorow card from the dicarded pile once per game. The same could go for a car for rockets or even the autocannon. maybe you would have to discard 2 cards to draw from the discard pile instead of the regular pile but only that type of weapon as allowed by your car. maybe you could even deal out 1 swerve card to each player before you suffled the cards. Giving a little more stratagy before using your card. Just some random thoughts for ya'll.
Working on those variant rules right now. Getting close to being finished.