Playing older and newer Forza titles back to back recently made me think about one particular thing: the current upgrade system with 3 “tiers” of parts (or 4 if we include stock) is kind of outdated. Don’t get me wrong, it does work, but there’s just something lacking.
In real life, it’s not just top-end parts that are adjustable on cars, many parts made for cars that only occasionally drive on tracks are adjustable. Even some stock parts in some real life cars are adjustable, for example the Mazda RX-7 FD Bathurst R has adjustable suspension by default. That’s why I think Forza should make more parts on cars adjustable, and they shouldn’t be sorted by “street”, “sports” and “race” names anymore, but by actual tier numbers, with varying levels of adjustability. This way, the equivalent of “street” suspension would have a small range of adjustability, “sports” equivalent would increase it a bit, “race” equivalent would increase it even more, and maybe there would finally be something above “race”. Forza already offers partial adjustability on one specific part, that is the differential, so why not widen the range of partial adjustability? This would go for all kinds of parts that feature it already, or maybe even more. We could finally see turbo adjustments, perhaps current assists like ABS, traction and launch control could finally become adjustable instead of binary “on and off” assists they’ve been since Motorsport 1.
One could say that GT7 already offers something like this and they would be correct, but I don’t see anything wrong with taking inspiration with that. In my opinion, this would be a lot more than just " a change for the sake of changing", as it wouldn’t just look different but also function differently.
Yea even on gran turismo 3 many low end part still gave adjustability just the sliders couldnt go as far.
I’m kind of sad that this hasn’t got pretty much any votes, yet I know it would improve the experience of many people, myself included.
I’ve thought of a way to draw more attention to our cause:
‘Free Hat’
Voted. 
I was just about to post something like this here, but I searched first & found you already suggested it.
Sport transmission has adjustable final drive.
Sport 1.5-way differential has adjustable acceleration %.
Sport brakes now have adjustable balance & strength.
…so can we have sport suspension with adjustable alignment (camber, toe, & caster) and ride height?
…And/or, as OP stated, can we have more adjustable settings in general on any/all parts?