You still need software support for it on the host device.
While you can imitate Keyboard and Mouse (and they would work through boot or without OS), Video is out of question for now.
And while there is still some value on it using on a healthy system, most of the time KVM device is needed when something is not working.
NB there is/was Intel ATM which provides (at least on paper and on rare, extremely rare posts on Internet) KVM-like experience and power control. Theoretically it can be used as the basis for single USB port KVM interface.
