They aren't a hard problem to solve. In the server market it's completely solved with a BMC. The problem being solved here is someone wants to make a product using some commodity product like a raspberry pi, perform video capture on a VGA/HMDI/DP port. This is not actually a problem end users have.

If you want to plug into a system that isn't server class, then they should be producing a video card that hooks into the USB bus, the always on rail of the power supply, the power switch pin of the power supply, and has an RJ45 jack. The contents of the card should be an off the shelf BMC chip.

But realistically if you want this kind of functionality, just buy server class systems that come with it.