First of, English isn't my native language. So I apologies for mistakes (grammar in particular) Like the title says, I think that can be a good things for this game. With 80+ cars and 20+ track, it can be easy to do this and be a better way to test content before buy. I suggest that because, sometime, when I try a car with the store, my FFB can be very lite and I don't know if the FFB multiplier works when I try a car. Same for the grip of the cars. Some of them just drift away when I try them and I can do nothing to see if it's just me who be a bad driver (and I'm not good) or if I can do something to have more grip ( no menu so no setup). That's really not the best way to test before buy. With a weekly content rotation (just like league of legend), we can see all this parameter and give us a better idea of cars nor tracks. I also think that can be a better things for new driver on this game. They can have a better idea of the content. (sorry if that's already be suggest. Near 5a.m when I post this and to tired for search ^^)
I like the idea, anything to bring more people in would be a great addition to the game. Though it sounds very difficult to accomplish - from reading the above it sounds like you want to rotate the free content. I dont know of any racing game that does that....tracks are tracks i dont see the point in rotating them, you either like them or you dont... thats my opinion ..and you do get to test drive the cars (last time i bought a car, has been a while) - and purchase the one skin if necessary which is around £2 for me....all in all i dont think the system is that bad, but sure there is always room for improvement
Imo test drive setup should be enabled as ingame and steering/ffb so you can drive it the way you like it. (Although some competitons you can enter without owning car IIRC but you would have to wait for car you want to drive if it is not in competiton at that time )