"nick" from Assetto Corsa is having the option to choose factory settings of the cars with regards to having Traction Control and ABS or not. Buggered if I know which cars really have traction control or not in real life. Just sayin'.
Yes it would be nice if this was an option in the setup screen in the car, with a button or encoder/switch to control it as well. This would be separate from the generic driver aids which apply to every car.
In certain street cars, if they come from the factory with these things then that's a good idea. If the race prepared version of that street car has all those things ripped out for a certain race series in real life than they shouldn't be available.
Just my opion on this: Some drivers don't like TC or ABS. So don't force it on them... I'm not that kind of a hardcore simracer, so i use it with some cars. With online races: "server-host" could just allow it more often, so it's up to the user to do with it what he likes. I don't want to force users to use TC or ABS. But in general when we allow it, when the cars have it IRL or if the cars or hard to handle. The racing is more fair/clean and closer ==> more fun. BTW: It's just a quick google search if cars have TC/ABS! And with the various live timing apps it's easy to see who used TC/ABS or not. So you can run a PRO and PRO/Am class easy in a league. But if your question is more levels of TC and ABS, Like the real GT cars. I say yes! implement it in the setup menu and/or toggle it with buttons in the car. But i don't think it's going to be a high priority at the moment. But a sure thing (i hope) for the future.