A couple of things related to this, since it seems not everyone is aware. The most common Klipper-compatible CAN boards (the BTT EBB36 and EBB42) are both USB/CAN – they can be used as a CAN toolboard, but can also be used directly via USB. You still have to run 12/24v power to them even if you’re using USB, but its vastly easier and cheaper to find continuous flex USB cables than it is to find affordable impedence-balanced continuous flex CAN wiring. (Proper CAN wiring can be $50-$100USD/m!)
A USB-PD version of those would be near perfect, but would require (as discussed above) a USB-PD injector board or microcontroller board with USB-C ports that support PD. (Even most desktop PCs don’t have that.)
I do think, however, using USB connectors with non-USB signals on them is a bad idea. Its a good way to have someone accidentally let the blue smoke out – and it could be from something expensive.
I’ve been working on a replacement toolboard for the Biqu Hermit Crab, because their CAN board has a bunch of dumb decisions made with it, and decided against USB-PD because USB-PD injectors are really expensive.