Something like this https://github.com/KovaaK/InterAccel
I love BTT, can't live without it, but on my ultrawide monitor I often wish I could move from one side to the other faster. If I fix that with speed I can't click on things reliably
so... customizable pointer acceleration curves
Just want to second this. I was thinking of moving to Apple's Magic Trackpad over my Kensington ExpertMouse (aka the billiard ball) which I've been using for decades, but the lack of acceleration control over movement is killing me. I have two 2K monitors with one 4K in the center. With the trackball I have very fine control over movement at slow speeds; perfect for text editing and drawing, but at the same time can whip the cursor from one side to the other with a single spin. I need that fine control at slow speeds, acceleration at higher speeds. But the closest I can come with BTT is to hold down a modifier to change the cursor speed, and that's way too much work for something which normally I don't even think about.