With USB-C this is a lot more likely, the main issue is going to be software support (Decent chance you could hack something up if one of the devices is running linux. No idea if anything exists for windows).
Could a smartphone sit between 2 regular laptops to achieve this with 3 USB cables and a hub ?
You would need a USB hub that could turn a USB device into two USB device ports, which I don't think exists. (hubs are essentially only a host-side thing).