There ok lots of upgrades and mods u can find online. There kinda the ones that got me into wanting to mod every RC I ever bought. You can check out the X-Mods website if its still up, the new ones suk bad they done even look like real cars or truck but the are bigger than the gen 1-2 so might be able to use model cars and truck body's for them not sure though haven't tried them yet.
That's an option too with these smaller scales you can pretty much be creative with some mods. It all depends on what you want. With mini-z's they have buttery smooth performance. Yes the bodies maybe non customizable but I've seen some crazy ways to modify them. You can always attach an xmod body I've done that before.