Get the tyre company make you a special run of their tyres with a different compound? There's a tweak. As for tweaking suspension, how do you tweak a linear leverage ratio bike blowing through the travel to run a coil shock if your rider requires it? And to drag out the argument to ridiculousness, it can't be done with a simple rocker link switch, as the shock is driven off the swingarm for example

Everything can be tweaked, if there is a strong enough wish. With tyres, the strongest tweak applicator is the humble sharpie. It has enabled running...