The part (or re-design) that is most needed is the front wheel hubs that are too open and prone to picking up dust and fibers. I know it can be done, because both the old Epoch 1/43 scales and smaller 1/64th that I tested long ago were never this bad in that respect.
Yes, the d'nano is much quicker and thus the wheels rotate faster ...so they pick up dust easier than the Epoch, but with all the clever engineering I've seen from the likes of PN Racing, Atomic, etc. ... someone could figure out a better front hub. And if they did, we could have this type of $200 carpet track ...
And then the 1/2 million strong slot car market would finally say ...hmmm, I gon'a try this.
So, if anyone has connections to these aftermarket engineers (and I know some of you do) I really think that this one upgrade/redesign would make a huge difference.