it's not all doom and gloom my friend, take heart!
sure, it is true that you cannot save in mid-championship.
however, what is stopping you from simply PAUSING THE GAME and leaving the PS3 running until you have your next opportunity to play?
i can tell you that that is how i have had to beat some of the more grueling races - if you think the Championship is a pain in your as*, then just wait until you get to the endurance races! 24 hours at a stretch? really? no way jose.
i just play as long as i can, pause the damn thing, and come back to it the next day. problem solved my friend - enjoy!
PS - oh and if for some reason you are worried about leaving the PS3 on overnight, don't be. i've had mine (fat one) running pretty much continiously for months at a time with zero issues.
best,
-d